Backend guides
Connect how clients talk to your server, how you model data, and how you keep services reliable and safe.
What do GET, POST, PUT, PATCH, and DELETE mean in REST-style APIs?
Map HTTP verbs to safe/idempotent behavior and when not to use GET for state changes.
httprestapi
What is a relational database and what does a basic SELECT do?
Tables, primary keys, and how SQL is the main language to query structured data in many backends.
sqldatabasepostgres
What are HTTP status codes 200, 201, 400, 401, 404, 500, and 503 in APIs?
Map codes to "success vs client error vs server error" so clients and logs stay understandable.
httpapierrors
What is the difference between authentication and authorization in a backend system?
Proving who you are vs deciding what you are allowed to do, often with sessions or tokens.
authsecurityjwt
What is caching in backend systems: HTTP Cache-Control, reverse proxies, and Redis?
Move work out of the hot path: browser caches, edge caches, in-memory data stores, and what can go wrong with stale data.
cachingredisperformance
What is a database transaction and what does ACID mean?
BEGIN, COMMIT, ROLLBACK: group work so it either fully applies or fully rolls back, with consistency rules.
sqltransactionspostgres