diff --git a/backend/app/core/config.py b/backend/app/core/config.py
index 43e1ec0..54c8f90 100644
--- a/backend/app/core/config.py
+++ b/backend/app/core/config.py
@@ -39,6 +39,32 @@ class Settings(BaseSettings):
     db_pool_timeout: int = 30  # Seconds to wait for a connection
     db_pool_recycle: int = 3600  # Recycle connections after 1 hour
 
+    # Redis configuration (Syndarix: cache, pub/sub, Celery broker)
+    REDIS_URL: str = Field(
+        default="redis://localhost:6379/0",
+        description="Redis URL for cache, pub/sub, and Celery broker",
+    )
+
+    # Celery configuration (Syndarix: background task processing)
+    CELERY_BROKER_URL: str | None = Field(
+        default=None,
+        description="Celery broker URL (defaults to REDIS_URL if not set)",
+    )
+    CELERY_RESULT_BACKEND: str | None = Field(
+        default=None,
+        description="Celery result backend URL (defaults to REDIS_URL if not set)",
+    )
+
+    @property
+    def celery_broker_url(self) -> str:
+        """Get Celery broker URL, defaulting to Redis."""
+        return self.CELERY_BROKER_URL or self.REDIS_URL
+
+    @property
+    def celery_result_backend(self) -> str:
+        """Get Celery result backend URL, defaulting to Redis."""
+        return self.CELERY_RESULT_BACKEND or self.REDIS_URL
+
     # SQL debugging (disable in production)
     sql_echo: bool = False  # Log SQL statements
     sql_echo_pool: bool = False  # Log connection pool events
diff --git a/backend/app/core/redis.py b/backend/app/core/redis.py
new file mode 100644
index 0000000..43da57b
--- /dev/null
+++ b/backend/app/core/redis.py
@@ -0,0 +1,476 @@
+# app/core/redis.py
+"""
+Redis client configuration for caching and pub/sub.
+
+This module provides async Redis connectivity with connection pooling
+for FastAPI endpoints and background tasks.
+
+Features:
+- Connection pooling for efficient resource usage
+- Cache operations (get, set, delete, expire)
+- Pub/sub operations (publish, subscribe)
+- Health check for monitoring
+"""
+
+import asyncio
+import json
+import logging
+from collections.abc import AsyncGenerator
+from contextlib import asynccontextmanager
+from typing import Any
+
+from redis.asyncio import ConnectionPool, Redis
+from redis.asyncio.client import PubSub
+from redis.exceptions import ConnectionError, RedisError, TimeoutError
+
+from app.core.config import settings
+
+# Configure logging
+logger = logging.getLogger(__name__)
+
+# Default TTL for cache entries (1 hour)
+DEFAULT_CACHE_TTL = 3600
+
+# Connection pool settings
+POOL_MAX_CONNECTIONS = 50
+POOL_TIMEOUT = 10  # seconds
+
+
+class RedisClient:
+    """
+    Async Redis client with connection pooling.
+
+    Provides high-level operations for caching and pub/sub
+    with proper error handling and connection management.
+    """
+
+    def __init__(self, url: str | None = None) -> None:
+        """
+        Initialize Redis client.
+
+        Args:
+            url: Redis connection URL. Defaults to settings.REDIS_URL.
+        """
+        self._url = url or settings.REDIS_URL
+        self._pool: ConnectionPool | None = None
+        self._client: Redis | None = None
+        self._lock = asyncio.Lock()
+
+    async def _ensure_pool(self) -> ConnectionPool:
+        """Ensure connection pool is initialized (thread-safe)."""
+        if self._pool is None:
+            async with self._lock:
+                # Double-check after acquiring lock
+                if self._pool is None:
+                    self._pool = ConnectionPool.from_url(
+                        self._url,
+                        max_connections=POOL_MAX_CONNECTIONS,
+                        socket_timeout=POOL_TIMEOUT,
+                        socket_connect_timeout=POOL_TIMEOUT,
+                        decode_responses=True,
+                        health_check_interval=30,
+                    )
+                    logger.info("Redis connection pool initialized")
+        return self._pool
+
+    async def _get_client(self) -> Redis:
+        """Get Redis client instance from pool."""
+        pool = await self._ensure_pool()
+        if self._client is None:
+            self._client = Redis(connection_pool=pool)
+        return self._client
+
+    # =========================================================================
+    # Cache Operations
+    # =========================================================================
+
+    async def cache_get(self, key: str) -> str | None:
+        """
+        Get a value from cache.
+
+        Args:
+            key: Cache key.
+
+        Returns:
+            Cached value or None if not found.
+        """
+        try:
+            client = await self._get_client()
+            value = await client.get(key)
+            if value is not None:
+                logger.debug(f"Cache hit for key: {key}")
+            else:
+                logger.debug(f"Cache miss for key: {key}")
+            return value
+        except (ConnectionError, TimeoutError) as e:
+            logger.error(f"Redis cache_get failed for key '{key}': {e}")
+            return None
+        except RedisError as e:
+            logger.error(f"Redis error in cache_get for key '{key}': {e}")
+            return None
+
+    async def cache_get_json(self, key: str) -> Any | None:
+        """
+        Get a JSON-serialized value from cache.
+
+        Args:
+            key: Cache key.
+
+        Returns:
+            Deserialized value or None if not found.
+        """
+        value = await self.cache_get(key)
+        if value is not None:
+            try:
+                return json.loads(value)
+            except json.JSONDecodeError as e:
+                logger.error(f"Failed to decode JSON for key '{key}': {e}")
+                return None
+        return None
+
+    async def cache_set(
+        self,
+        key: str,
+        value: str,
+        ttl: int | None = None,
+    ) -> bool:
+        """
+        Set a value in cache.
+
+        Args:
+            key: Cache key.
+            value: Value to cache.
+            ttl: Time-to-live in seconds. Defaults to DEFAULT_CACHE_TTL.
+
+        Returns:
+            True if successful, False otherwise.
+        """
+        try:
+            client = await self._get_client()
+            ttl = ttl if ttl is not None else DEFAULT_CACHE_TTL
+            await client.set(key, value, ex=ttl)
+            logger.debug(f"Cache set for key: {key} (TTL: {ttl}s)")
+            return True
+        except (ConnectionError, TimeoutError) as e:
+            logger.error(f"Redis cache_set failed for key '{key}': {e}")
+            return False
+        except RedisError as e:
+            logger.error(f"Redis error in cache_set for key '{key}': {e}")
+            return False
+
+    async def cache_set_json(
+        self,
+        key: str,
+        value: Any,
+        ttl: int | None = None,
+    ) -> bool:
+        """
+        Set a JSON-serialized value in cache.
+
+        Args:
+            key: Cache key.
+            value: Value to serialize and cache.
+            ttl: Time-to-live in seconds.
+
+        Returns:
+            True if successful, False otherwise.
+        """
+        try:
+            serialized = json.dumps(value)
+            return await self.cache_set(key, serialized, ttl)
+        except (TypeError, ValueError) as e:
+            logger.error(f"Failed to serialize value for key '{key}': {e}")
+            return False
+
+    async def cache_delete(self, key: str) -> bool:
+        """
+        Delete a key from cache.
+
+        Args:
+            key: Cache key to delete.
+
+        Returns:
+            True if key was deleted, False otherwise.
+        """
+        try:
+            client = await self._get_client()
+            result = await client.delete(key)
+            logger.debug(f"Cache delete for key: {key} (deleted: {result > 0})")
+            return result > 0
+        except (ConnectionError, TimeoutError) as e:
+            logger.error(f"Redis cache_delete failed for key '{key}': {e}")
+            return False
+        except RedisError as e:
+            logger.error(f"Redis error in cache_delete for key '{key}': {e}")
+            return False
+
+    async def cache_delete_pattern(self, pattern: str) -> int:
+        """
+        Delete all keys matching a pattern.
+
+        Args:
+            pattern: Glob-style pattern (e.g., "user:*").
+
+        Returns:
+            Number of keys deleted.
+        """
+        try:
+            client = await self._get_client()
+            deleted = 0
+            async for key in client.scan_iter(pattern):
+                await client.delete(key)
+                deleted += 1
+            logger.debug(f"Cache delete pattern '{pattern}': {deleted} keys deleted")
+            return deleted
+        except (ConnectionError, TimeoutError) as e:
+            logger.error(f"Redis cache_delete_pattern failed for '{pattern}': {e}")
+            return 0
+        except RedisError as e:
+            logger.error(f"Redis error in cache_delete_pattern for '{pattern}': {e}")
+            return 0
+
+    async def cache_expire(self, key: str, ttl: int) -> bool:
+        """
+        Set or update TTL for a key.
+
+        Args:
+            key: Cache key.
+            ttl: New TTL in seconds.
+
+        Returns:
+            True if TTL was set, False if key doesn't exist.
+        """
+        try:
+            client = await self._get_client()
+            result = await client.expire(key, ttl)
+            logger.debug(f"Cache expire for key: {key} (TTL: {ttl}s, success: {result})")
+            return result
+        except (ConnectionError, TimeoutError) as e:
+            logger.error(f"Redis cache_expire failed for key '{key}': {e}")
+            return False
+        except RedisError as e:
+            logger.error(f"Redis error in cache_expire for key '{key}': {e}")
+            return False
+
+    async def cache_exists(self, key: str) -> bool:
+        """
+        Check if a key exists in cache.
+
+        Args:
+            key: Cache key.
+
+        Returns:
+            True if key exists, False otherwise.
+        """
+        try:
+            client = await self._get_client()
+            result = await client.exists(key)
+            return result > 0
+        except (ConnectionError, TimeoutError) as e:
+            logger.error(f"Redis cache_exists failed for key '{key}': {e}")
+            return False
+        except RedisError as e:
+            logger.error(f"Redis error in cache_exists for key '{key}': {e}")
+            return False
+
+    async def cache_ttl(self, key: str) -> int:
+        """
+        Get remaining TTL for a key.
+
+        Args:
+            key: Cache key.
+
+        Returns:
+            TTL in seconds, -1 if no TTL, -2 if key doesn't exist.
+        """
+        try:
+            client = await self._get_client()
+            return await client.ttl(key)
+        except (ConnectionError, TimeoutError) as e:
+            logger.error(f"Redis cache_ttl failed for key '{key}': {e}")
+            return -2
+        except RedisError as e:
+            logger.error(f"Redis error in cache_ttl for key '{key}': {e}")
+            return -2
+
+    # =========================================================================
+    # Pub/Sub Operations
+    # =========================================================================
+
+    async def publish(self, channel: str, message: str | dict) -> int:
+        """
+        Publish a message to a channel.
+
+        Args:
+            channel: Channel name.
+            message: Message to publish (string or dict for JSON serialization).
+
+        Returns:
+            Number of subscribers that received the message.
+        """
+        try:
+            client = await self._get_client()
+            if isinstance(message, dict):
+                message = json.dumps(message)
+            result = await client.publish(channel, message)
+            logger.debug(f"Published to channel '{channel}': {result} subscribers")
+            return result
+        except (ConnectionError, TimeoutError) as e:
+            logger.error(f"Redis publish failed for channel '{channel}': {e}")
+            return 0
+        except RedisError as e:
+            logger.error(f"Redis error in publish for channel '{channel}': {e}")
+            return 0
+
+    @asynccontextmanager
+    async def subscribe(
+        self, *channels: str
+    ) -> AsyncGenerator[PubSub, None]:
+        """
+        Subscribe to one or more channels.
+
+        Usage:
+            async with redis_client.subscribe("channel1", "channel2") as pubsub:
+                async for message in pubsub.listen():
+                    if message["type"] == "message":
+                        print(message["data"])
+
+        Args:
+            channels: Channel names to subscribe to.
+
+        Yields:
+            PubSub instance for receiving messages.
+        """
+        client = await self._get_client()
+        pubsub = client.pubsub()
+        try:
+            await pubsub.subscribe(*channels)
+            logger.debug(f"Subscribed to channels: {channels}")
+            yield pubsub
+        finally:
+            await pubsub.unsubscribe(*channels)
+            await pubsub.close()
+            logger.debug(f"Unsubscribed from channels: {channels}")
+
+    @asynccontextmanager
+    async def psubscribe(
+        self, *patterns: str
+    ) -> AsyncGenerator[PubSub, None]:
+        """
+        Subscribe to channels matching patterns.
+
+        Usage:
+            async with redis_client.psubscribe("user:*") as pubsub:
+                async for message in pubsub.listen():
+                    if message["type"] == "pmessage":
+                        print(message["pattern"], message["channel"], message["data"])
+
+        Args:
+            patterns: Glob-style patterns to subscribe to.
+
+        Yields:
+            PubSub instance for receiving messages.
+        """
+        client = await self._get_client()
+        pubsub = client.pubsub()
+        try:
+            await pubsub.psubscribe(*patterns)
+            logger.debug(f"Pattern subscribed: {patterns}")
+            yield pubsub
+        finally:
+            await pubsub.punsubscribe(*patterns)
+            await pubsub.close()
+            logger.debug(f"Pattern unsubscribed: {patterns}")
+
+    # =========================================================================
+    # Health & Connection Management
+    # =========================================================================
+
+    async def health_check(self) -> bool:
+        """
+        Check if Redis connection is healthy.
+
+        Returns:
+            True if connection is successful, False otherwise.
+        """
+        try:
+            client = await self._get_client()
+            result = await client.ping()
+            return result is True
+        except (ConnectionError, TimeoutError) as e:
+            logger.error(f"Redis health check failed: {e}")
+            return False
+        except RedisError as e:
+            logger.error(f"Redis health check error: {e}")
+            return False
+
+    async def close(self) -> None:
+        """
+        Close Redis connections and cleanup resources.
+
+        Should be called during application shutdown.
+        """
+        if self._client:
+            await self._client.close()
+            self._client = None
+            logger.debug("Redis client closed")
+
+        if self._pool:
+            await self._pool.disconnect()
+            self._pool = None
+            logger.info("Redis connection pool closed")
+
+    async def get_pool_info(self) -> dict[str, Any]:
+        """
+        Get connection pool statistics.
+
+        Returns:
+            Dictionary with pool information.
+        """
+        if self._pool is None:
+            return {"status": "not_initialized"}
+
+        return {
+            "status": "active",
+            "max_connections": POOL_MAX_CONNECTIONS,
+            "url": self._url.split("@")[-1] if "@" in self._url else self._url,
+        }
+
+
+# Global Redis client instance
+redis_client = RedisClient()
+
+
+# FastAPI dependency for Redis client
+async def get_redis() -> AsyncGenerator[RedisClient, None]:
+    """
+    FastAPI dependency that provides the Redis client.
+
+    Usage:
+        @router.get("/cached-data")
+        async def get_data(redis: RedisClient = Depends(get_redis)):
+            cached = await redis.cache_get("my-key")
+            ...
+    """
+    yield redis_client
+
+
+# Health check function for use in /health endpoint
+async def check_redis_health() -> bool:
+    """
+    Check if Redis connection is healthy.
+
+    Returns:
+        True if connection is successful, False otherwise.
+    """
+    return await redis_client.health_check()
+
+
+# Cleanup function for application shutdown
+async def close_redis() -> None:
+    """
+    Close Redis connections.
+
+    Should be called during application shutdown.
+    """
+    await redis_client.close()
diff --git a/backend/tests/core/test_redis.py b/backend/tests/core/test_redis.py
new file mode 100644
index 0000000..58214e8
--- /dev/null
+++ b/backend/tests/core/test_redis.py
@@ -0,0 +1,784 @@
+"""
+Tests for Redis client utility functions (app/core/redis.py).
+
+Covers:
+- Cache operations (get, set, delete, expire)
+- JSON serialization helpers
+- Pub/sub operations
+- Health check
+- Connection pooling
+- Error handling
+"""
+
+import asyncio
+import json
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+from redis.exceptions import ConnectionError, RedisError, TimeoutError
+
+from app.core.redis import (
+    DEFAULT_CACHE_TTL,
+    POOL_MAX_CONNECTIONS,
+    RedisClient,
+    check_redis_health,
+    close_redis,
+    get_redis,
+    redis_client,
+)
+
+
+class TestRedisClientInit:
+    """Test RedisClient initialization."""
+
+    def test_default_url_from_settings(self):
+        """Test that default URL comes from settings."""
+        with patch("app.core.redis.settings") as mock_settings:
+            mock_settings.REDIS_URL = "redis://test:6379/0"
+            client = RedisClient()
+            assert client._url == "redis://test:6379/0"
+
+    def test_custom_url_override(self):
+        """Test that custom URL overrides settings."""
+        client = RedisClient(url="redis://custom:6379/1")
+        assert client._url == "redis://custom:6379/1"
+
+    def test_initial_state(self):
+        """Test initial client state."""
+        client = RedisClient(url="redis://localhost:6379/0")
+        assert client._pool is None
+        assert client._client is None
+
+
+class TestCacheOperations:
+    """Test cache get/set/delete operations."""
+
+    @pytest.mark.asyncio
+    async def test_cache_set_success(self):
+        """Test setting a cache value."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.set = AsyncMock(return_value=True)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_set("test-key", "test-value", ttl=60)
+
+        assert result is True
+        mock_redis.set.assert_called_once_with("test-key", "test-value", ex=60)
+
+    @pytest.mark.asyncio
+    async def test_cache_set_default_ttl(self):
+        """Test setting a cache value with default TTL."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.set = AsyncMock(return_value=True)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_set("test-key", "test-value")
+
+        assert result is True
+        mock_redis.set.assert_called_once_with(
+            "test-key", "test-value", ex=DEFAULT_CACHE_TTL
+        )
+
+    @pytest.mark.asyncio
+    async def test_cache_set_connection_error(self):
+        """Test cache_set handles connection errors."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.set = AsyncMock(side_effect=ConnectionError("Connection refused"))
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_set("test-key", "test-value")
+
+        assert result is False
+
+    @pytest.mark.asyncio
+    async def test_cache_set_timeout_error(self):
+        """Test cache_set handles timeout errors."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.set = AsyncMock(side_effect=TimeoutError("Timeout"))
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_set("test-key", "test-value")
+
+        assert result is False
+
+    @pytest.mark.asyncio
+    async def test_cache_set_redis_error(self):
+        """Test cache_set handles generic Redis errors."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.set = AsyncMock(side_effect=RedisError("Unknown error"))
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_set("test-key", "test-value")
+
+        assert result is False
+
+    @pytest.mark.asyncio
+    async def test_cache_get_success(self):
+        """Test getting a cached value."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.get = AsyncMock(return_value="cached-value")
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_get("test-key")
+
+        assert result == "cached-value"
+        mock_redis.get.assert_called_once_with("test-key")
+
+    @pytest.mark.asyncio
+    async def test_cache_get_miss(self):
+        """Test cache miss returns None."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.get = AsyncMock(return_value=None)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_get("nonexistent-key")
+
+        assert result is None
+
+    @pytest.mark.asyncio
+    async def test_cache_get_connection_error(self):
+        """Test cache_get handles connection errors."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.get = AsyncMock(side_effect=ConnectionError("Connection refused"))
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_get("test-key")
+
+        assert result is None
+
+    @pytest.mark.asyncio
+    async def test_cache_delete_success(self):
+        """Test deleting a cache key."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.delete = AsyncMock(return_value=1)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_delete("test-key")
+
+        assert result is True
+        mock_redis.delete.assert_called_once_with("test-key")
+
+    @pytest.mark.asyncio
+    async def test_cache_delete_nonexistent_key(self):
+        """Test deleting a nonexistent key returns False."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.delete = AsyncMock(return_value=0)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_delete("nonexistent-key")
+
+        assert result is False
+
+    @pytest.mark.asyncio
+    async def test_cache_delete_connection_error(self):
+        """Test cache_delete handles connection errors."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.delete = AsyncMock(side_effect=ConnectionError("Connection refused"))
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_delete("test-key")
+
+        assert result is False
+
+
+class TestCacheDeletePattern:
+    """Test cache_delete_pattern operation."""
+
+    @pytest.mark.asyncio
+    async def test_cache_delete_pattern_success(self):
+        """Test deleting keys by pattern."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.delete = AsyncMock(return_value=1)
+
+        # Create async iterator for scan_iter
+        async def mock_scan_iter(pattern):
+            for key in ["user:1", "user:2", "user:3"]:
+                yield key
+
+        mock_redis.scan_iter = mock_scan_iter
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_delete_pattern("user:*")
+
+        assert result == 3
+        assert mock_redis.delete.call_count == 3
+
+    @pytest.mark.asyncio
+    async def test_cache_delete_pattern_no_matches(self):
+        """Test deleting pattern with no matches."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+
+        async def mock_scan_iter(pattern):
+            if False:  # Empty iterator
+                yield
+
+        mock_redis.scan_iter = mock_scan_iter
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_delete_pattern("nonexistent:*")
+
+        assert result == 0
+
+    @pytest.mark.asyncio
+    async def test_cache_delete_pattern_error(self):
+        """Test cache_delete_pattern handles errors."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+
+        async def mock_scan_iter(pattern):
+            raise ConnectionError("Connection lost")
+            if False:  # Make it a generator
+                yield
+
+        mock_redis.scan_iter = mock_scan_iter
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_delete_pattern("user:*")
+
+        assert result == 0
+
+
+class TestCacheExpire:
+    """Test cache_expire operation."""
+
+    @pytest.mark.asyncio
+    async def test_cache_expire_success(self):
+        """Test setting TTL on existing key."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.expire = AsyncMock(return_value=True)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_expire("test-key", 120)
+
+        assert result is True
+        mock_redis.expire.assert_called_once_with("test-key", 120)
+
+    @pytest.mark.asyncio
+    async def test_cache_expire_nonexistent_key(self):
+        """Test setting TTL on nonexistent key."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.expire = AsyncMock(return_value=False)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_expire("nonexistent-key", 120)
+
+        assert result is False
+
+    @pytest.mark.asyncio
+    async def test_cache_expire_error(self):
+        """Test cache_expire handles errors."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.expire = AsyncMock(side_effect=ConnectionError("Error"))
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_expire("test-key", 120)
+
+        assert result is False
+
+
+class TestCacheHelpers:
+    """Test cache helper methods (exists, ttl)."""
+
+    @pytest.mark.asyncio
+    async def test_cache_exists_true(self):
+        """Test cache_exists returns True for existing key."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.exists = AsyncMock(return_value=1)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_exists("test-key")
+
+        assert result is True
+
+    @pytest.mark.asyncio
+    async def test_cache_exists_false(self):
+        """Test cache_exists returns False for nonexistent key."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.exists = AsyncMock(return_value=0)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_exists("nonexistent-key")
+
+        assert result is False
+
+    @pytest.mark.asyncio
+    async def test_cache_exists_error(self):
+        """Test cache_exists handles errors."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.exists = AsyncMock(side_effect=ConnectionError("Error"))
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_exists("test-key")
+
+        assert result is False
+
+    @pytest.mark.asyncio
+    async def test_cache_ttl_with_ttl(self):
+        """Test cache_ttl returns remaining TTL."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.ttl = AsyncMock(return_value=300)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_ttl("test-key")
+
+        assert result == 300
+
+    @pytest.mark.asyncio
+    async def test_cache_ttl_no_ttl(self):
+        """Test cache_ttl returns -1 for key without TTL."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.ttl = AsyncMock(return_value=-1)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_ttl("test-key")
+
+        assert result == -1
+
+    @pytest.mark.asyncio
+    async def test_cache_ttl_nonexistent_key(self):
+        """Test cache_ttl returns -2 for nonexistent key."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.ttl = AsyncMock(return_value=-2)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_ttl("nonexistent-key")
+
+        assert result == -2
+
+    @pytest.mark.asyncio
+    async def test_cache_ttl_error(self):
+        """Test cache_ttl handles errors."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.ttl = AsyncMock(side_effect=ConnectionError("Error"))
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_ttl("test-key")
+
+        assert result == -2
+
+
+class TestJsonOperations:
+    """Test JSON serialization cache operations."""
+
+    @pytest.mark.asyncio
+    async def test_cache_set_json_success(self):
+        """Test setting a JSON value in cache."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.set = AsyncMock(return_value=True)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            data = {"user": "test", "count": 42}
+            result = await client.cache_set_json("test-key", data, ttl=60)
+
+        assert result is True
+        mock_redis.set.assert_called_once()
+        # Verify JSON was serialized
+        call_args = mock_redis.set.call_args
+        assert call_args[0][1] == json.dumps(data)
+
+    @pytest.mark.asyncio
+    async def test_cache_set_json_serialization_error(self):
+        """Test cache_set_json handles serialization errors."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        # Object that can't be serialized
+        class NonSerializable:
+            pass
+
+        result = await client.cache_set_json("test-key", NonSerializable())
+        assert result is False
+
+    @pytest.mark.asyncio
+    async def test_cache_get_json_success(self):
+        """Test getting a JSON value from cache."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        data = {"user": "test", "count": 42}
+        mock_redis.get = AsyncMock(return_value=json.dumps(data))
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_get_json("test-key")
+
+        assert result == data
+
+    @pytest.mark.asyncio
+    async def test_cache_get_json_miss(self):
+        """Test cache_get_json returns None on cache miss."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.get = AsyncMock(return_value=None)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_get_json("nonexistent-key")
+
+        assert result is None
+
+    @pytest.mark.asyncio
+    async def test_cache_get_json_invalid_json(self):
+        """Test cache_get_json handles invalid JSON."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.get = AsyncMock(return_value="not valid json {{{")
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.cache_get_json("test-key")
+
+        assert result is None
+
+
+class TestPubSubOperations:
+    """Test pub/sub operations."""
+
+    @pytest.mark.asyncio
+    async def test_publish_string_message(self):
+        """Test publishing a string message."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.publish = AsyncMock(return_value=2)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.publish("test-channel", "hello world")
+
+        assert result == 2
+        mock_redis.publish.assert_called_once_with("test-channel", "hello world")
+
+    @pytest.mark.asyncio
+    async def test_publish_dict_message(self):
+        """Test publishing a dict message (JSON serialized)."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.publish = AsyncMock(return_value=1)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            data = {"event": "user_created", "user_id": 123}
+            result = await client.publish("events", data)
+
+        assert result == 1
+        mock_redis.publish.assert_called_once_with("events", json.dumps(data))
+
+    @pytest.mark.asyncio
+    async def test_publish_connection_error(self):
+        """Test publish handles connection errors."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.publish = AsyncMock(side_effect=ConnectionError("Connection lost"))
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.publish("test-channel", "hello")
+
+        assert result == 0
+
+    @pytest.mark.asyncio
+    async def test_subscribe_context_manager(self):
+        """Test subscribe context manager."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_pubsub = AsyncMock()
+        mock_pubsub.subscribe = AsyncMock()
+        mock_pubsub.unsubscribe = AsyncMock()
+        mock_pubsub.close = AsyncMock()
+
+        mock_redis = AsyncMock()
+        mock_redis.pubsub = MagicMock(return_value=mock_pubsub)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            async with client.subscribe("channel1", "channel2") as pubsub:
+                assert pubsub is mock_pubsub
+                mock_pubsub.subscribe.assert_called_once_with("channel1", "channel2")
+
+            # After exiting context, should unsubscribe and close
+            mock_pubsub.unsubscribe.assert_called_once_with("channel1", "channel2")
+            mock_pubsub.close.assert_called_once()
+
+    @pytest.mark.asyncio
+    async def test_psubscribe_context_manager(self):
+        """Test pattern subscribe context manager."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_pubsub = AsyncMock()
+        mock_pubsub.psubscribe = AsyncMock()
+        mock_pubsub.punsubscribe = AsyncMock()
+        mock_pubsub.close = AsyncMock()
+
+        mock_redis = AsyncMock()
+        mock_redis.pubsub = MagicMock(return_value=mock_pubsub)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            async with client.psubscribe("user:*", "event:*") as pubsub:
+                assert pubsub is mock_pubsub
+                mock_pubsub.psubscribe.assert_called_once_with("user:*", "event:*")
+
+            mock_pubsub.punsubscribe.assert_called_once_with("user:*", "event:*")
+            mock_pubsub.close.assert_called_once()
+
+
+class TestHealthCheck:
+    """Test health check functionality."""
+
+    @pytest.mark.asyncio
+    async def test_health_check_success(self):
+        """Test health check returns True when Redis is healthy."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.ping = AsyncMock(return_value=True)
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.health_check()
+
+        assert result is True
+        mock_redis.ping.assert_called_once()
+
+    @pytest.mark.asyncio
+    async def test_health_check_connection_error(self):
+        """Test health check returns False on connection error."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.ping = AsyncMock(side_effect=ConnectionError("Connection refused"))
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.health_check()
+
+        assert result is False
+
+    @pytest.mark.asyncio
+    async def test_health_check_timeout_error(self):
+        """Test health check returns False on timeout."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.ping = AsyncMock(side_effect=TimeoutError("Timeout"))
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.health_check()
+
+        assert result is False
+
+    @pytest.mark.asyncio
+    async def test_health_check_redis_error(self):
+        """Test health check returns False on Redis error."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_redis = AsyncMock()
+        mock_redis.ping = AsyncMock(side_effect=RedisError("Unknown error"))
+
+        with patch.object(client, "_get_client", return_value=mock_redis):
+            result = await client.health_check()
+
+        assert result is False
+
+
+class TestConnectionPooling:
+    """Test connection pooling functionality."""
+
+    @pytest.mark.asyncio
+    async def test_pool_initialization(self):
+        """Test that pool is lazily initialized."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        assert client._pool is None
+
+        with patch("app.core.redis.ConnectionPool") as MockPool:
+            mock_pool = MagicMock()
+            MockPool.from_url = MagicMock(return_value=mock_pool)
+
+            pool = await client._ensure_pool()
+
+            assert pool is mock_pool
+            MockPool.from_url.assert_called_once_with(
+                "redis://localhost:6379/0",
+                max_connections=POOL_MAX_CONNECTIONS,
+                socket_timeout=10,
+                socket_connect_timeout=10,
+                decode_responses=True,
+                health_check_interval=30,
+            )
+
+    @pytest.mark.asyncio
+    async def test_pool_reuses_existing(self):
+        """Test that pool is reused after initialization."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_pool = MagicMock()
+        client._pool = mock_pool
+
+        pool = await client._ensure_pool()
+
+        assert pool is mock_pool
+
+    @pytest.mark.asyncio
+    async def test_close_disposes_resources(self):
+        """Test that close() disposes pool and client."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        mock_client = AsyncMock()
+        mock_pool = AsyncMock()
+        mock_pool.disconnect = AsyncMock()
+
+        client._client = mock_client
+        client._pool = mock_pool
+
+        await client.close()
+
+        mock_client.close.assert_called_once()
+        mock_pool.disconnect.assert_called_once()
+        assert client._client is None
+        assert client._pool is None
+
+    @pytest.mark.asyncio
+    async def test_close_handles_none(self):
+        """Test that close() handles None client and pool gracefully."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        # Should not raise
+        await client.close()
+
+        assert client._client is None
+        assert client._pool is None
+
+    @pytest.mark.asyncio
+    async def test_get_pool_info_not_initialized(self):
+        """Test pool info when not initialized."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        info = await client.get_pool_info()
+
+        assert info == {"status": "not_initialized"}
+
+    @pytest.mark.asyncio
+    async def test_get_pool_info_active(self):
+        """Test pool info when active."""
+        client = RedisClient(url="redis://user:pass@localhost:6379/0")
+
+        mock_pool = MagicMock()
+        client._pool = mock_pool
+
+        info = await client.get_pool_info()
+
+        assert info["status"] == "active"
+        assert info["max_connections"] == POOL_MAX_CONNECTIONS
+        # Password should be hidden
+        assert "pass" not in info["url"]
+        assert "localhost:6379/0" in info["url"]
+
+
+class TestModuleLevelFunctions:
+    """Test module-level convenience functions."""
+
+    @pytest.mark.asyncio
+    async def test_get_redis_dependency(self):
+        """Test get_redis FastAPI dependency."""
+        redis_gen = get_redis()
+
+        client = await redis_gen.__anext__()
+        assert client is redis_client
+
+        # Cleanup
+        with pytest.raises(StopAsyncIteration):
+            await redis_gen.__anext__()
+
+    @pytest.mark.asyncio
+    async def test_check_redis_health(self):
+        """Test module-level check_redis_health function."""
+        with patch.object(redis_client, "health_check", return_value=True) as mock:
+            result = await check_redis_health()
+
+        assert result is True
+        mock.assert_called_once()
+
+    @pytest.mark.asyncio
+    async def test_close_redis(self):
+        """Test module-level close_redis function."""
+        with patch.object(redis_client, "close") as mock:
+            await close_redis()
+
+        mock.assert_called_once()
+
+
+class TestThreadSafety:
+    """Test thread-safety of pool initialization."""
+
+    @pytest.mark.asyncio
+    async def test_concurrent_pool_initialization(self):
+        """Test that concurrent _ensure_pool calls create only one pool."""
+        client = RedisClient(url="redis://localhost:6379/0")
+
+        call_count = 0
+        mock_pool = MagicMock()
+
+        def counting_from_url(*args, **kwargs):
+            nonlocal call_count
+            call_count += 1
+            return mock_pool
+
+        with patch("app.core.redis.ConnectionPool") as MockPool:
+            MockPool.from_url = MagicMock(side_effect=counting_from_url)
+
+            # Start multiple concurrent _ensure_pool calls
+            results = await asyncio.gather(
+                client._ensure_pool(),
+                client._ensure_pool(),
+                client._ensure_pool(),
+            )
+
+        # All results should be the same pool instance
+        assert results[0] is results[1] is results[2]
+        assert results[0] is mock_pool
+        # Pool should only be created once despite concurrent calls
+        assert call_count == 1