Redis: Complete Course

What is Redis and why use it instead of a database

in-memory data store, key-value model, Redis vs relational DB, Redis vs Memcached, use cases, persistence overview

How to install Redis on Linux, macOS, and Docker

apt install, Homebrew install, Docker run, redis-server, redis-cli, default port 6379, config file location

Redis data types overview: strings, hashes, lists, sets, sorted sets

string type, hash type, list type, set type, sorted set type, TYPE command, choosing the right type

Redis key expiry and TTL: how to set and check expiration

EXPIRE, EXPIREAT, TTL, PERSIST, key eviction, expiry use cases, EX option on SET

Redis persistence: RDB snapshots vs AOF logging explained

RDB snapshot, AOF append-only file, BGSAVE, AOF rewrite, durability tradeoffs, redis.conf persistence settings, no persistence mode

Redis String commands: SET, GET, INCR, APPEND, GETRANGE

SET options NX EX PX, GET, MSET MGET, INCR INCRBY DECR, APPEND, GETRANGE, STRLEN, atomic counter pattern

Redis Hash commands: HSET, HGET, HMGET, HDEL, HGETALL

HSET multiple fields, HGET, HMGET, HGETALL, HDEL, HEXISTS, HLEN, HINCRBY, hash vs string tradeoffs

Redis List commands: LPUSH, RPUSH, LPOP, LRANGE, LLEN

LPUSH RPUSH, LPOP RPOP, LRANGE, LLEN, LINDEX, LSET, LTRIM, blocking BLPOP, queue vs stack pattern

Redis Set commands: SADD, SMEMBERS, SINTER, SUNION, SDIFF

SADD SREM, SMEMBERS SCARD, SISMEMBER, SINTER SUNION SDIFF, SMOVE, unique visitor tracking, tag systems

Redis Sorted Set commands: ZADD, ZRANGE, ZRANK, ZSCORE, ZRANGEBYSCORE

ZADD options NX XX GT LT, ZRANGE ZREVRANGE, ZRANK ZREVRANK, ZSCORE, ZRANGEBYSCORE, ZREM, ZINCRBY, leaderboard pattern

Cache-aside pattern: how to implement read-through caching in Node.js

cache-aside pattern, cache miss, cache hit, read-through vs write-through, TTL strategy, cache stampede risk, stale data tradeoff

Write-through and write-behind caching: when to update Redis on writes

write-through pattern, write-behind pattern, consistency tradeoff, dual write, cache invalidation, write amplification

Cache invalidation strategies: TTL, event-based, and tag-based invalidation

TTL-based invalidation, explicit delete on write, tag-based invalidation, cache key namespacing, versioned cache keys, invalidation fan-out problem

Redis cache eviction policies: LRU, LFU, and allkeys explained

maxmemory config, allkeys-lru, volatile-lru, allkeys-lfu, volatile-lfu, noeviction, allkeys-random, choosing eviction policy

Preventing cache stampede with Redis locks and probabilistic early expiration

cache stampede definition, mutex lock with SET NX, lock timeout, probabilistic early expiration algorithm, XFetch formula, dog-pile effect

Redis Pub/Sub: how PUBLISH and SUBSCRIBE work

PUBLISH command, SUBSCRIBE command, channel model, fire-and-forget semantics, no message persistence, multiple subscribers, PSUBSCRIBE pattern matching

Redis Streams introduction: durable append-only event logs

XADD command, stream entry ID, XLEN, XRANGE, XREAD, auto-generated IDs, stream as event log, difference from Pub/Sub

Redis Stream consumer groups: reliable message processing with XACK

XGROUP CREATE, XREADGROUP, XACK, pending entries list, consumer group semantics, at-least-once delivery, XCLAIM for stuck messages

Keyspace notifications: subscribe to Redis events like key expiry

keyspace notifications config, notify-keyspace-events, KEA flags, expired event, set event, del event, use cases for expiry hooks

When to use Pub/Sub vs Streams vs a job queue in Redis

Pub/Sub vs Streams decision criteria, message durability, fan-out delivery, consumer groups, BullMQ and Redis Lists as queues, at-most-once vs at-least-once

Redis transactions with MULTI and EXEC: atomic command batches

MULTI, EXEC, DISCARD, command queuing, all-or-nothing execution, error handling in transactions, no rollback on runtime errors

WATCH and optimistic locking in Redis: how to handle concurrent updates

WATCH command, optimistic locking, CAS pattern, MULTI after WATCH, EXEC returning nil on conflict, retry loop, WATCH vs pessimistic locking

Redis pipelines: batch commands to reduce network round trips

pipeline concept, round trip time, pipelining vs transactions, pipeline in Node.js, pipeline in Python, when to use pipelines, throughput benchmark

Lua scripting in Redis: run server-side logic atomically with EVAL

EVAL command, KEYS and ARGV, atomicity of Lua scripts, no interleaving, redis.call vs redis.pcall, SCRIPT LOAD EVALSHA, when to use Lua

Rate limiting with Redis: sliding window and token bucket patterns

rate limiting use case, fixed window counter, sliding window log with Sorted Set, token bucket with INCR and TTL, MULTI/EXEC for atomicity, rate limit headers

Redis replication: primary-replica setup and how replication works

primary-replica architecture, REPLICAOF command, full resync, partial resync, replication offset, read scaling with replicas, replication lag, async replication caveat

Redis Sentinel: automatic failover and high availability explained

Sentinel process, quorum, leader election, failover process, client reconfiguration, sentinel.conf, minimum 3 sentinels rule

Redis Cluster: horizontal sharding and how data is distributed

hash slot concept, 16384 slots, CRC16 key hashing, node assignment, CLUSTER INFO, hash tags, MOVED redirect, ASK redirect, minimum 3 primary nodes

Redis security: authentication, TLS, and ACL user permissions

requirepass, AUTH command, ACL LIST, ACL SETUSER, channel permissions, key pattern permissions, TLS configuration, binding to localhost, RENAME-COMMAND

Monitoring Redis with INFO, MONITOR, SLOWLOG, and latency commands

INFO sections, DBSIZE, MONITOR command, SLOWLOG GET, slowlog-log-slower-than, LATENCY HISTORY, memory usage analysis, redis-cli --stat, OBJECT FREQ for LFU