What is Redis and why is it popular in modern applications?

Redis is an in-memory data structure store that serves as: • **Database**: NoSQL key-value store • **Cache**: High-performance caching layer • **Message broker**: Pub/Sub messaging system **Why Popular:** • Extremely fast (100,000+ ops/sec) • Rich data types (strings, lists, sets, hashes) • Atomic operations • Built-in replication • Lua scripting support **Common Use Cases:** # Session storage SET session:user123 '{"name":"John", "role":"admin"}' EXPIRE session:user123 3600 # Caching SET cache:product:456 '{"name":"Laptop", "price":999}' # Counters INCR page:views:homepage