How does Redis differ from PostgreSQL? How is data stored in each?

Redis is an in-memory key-value data store focused on high-speed operations and support for data structures (strings, lists, sets, hashes, etc.). Data is stored in RAM, which provides very fast access, and can be periodically saved to disk for durability.

PostgreSQL is a relational database management system that stores data on disk in the form of tables with a clearly defined schema and supports complex SQL queries, transactions, indexes, etc.

Summary:

• Redis stores data in memory, suitable for caching, sessions, and fast operations.
• PostgreSQL stores data on disk, providing long-term storage and complex queries with integrity guarantees.