Backend 0 → PRO

Layering: controllers/services/repositories ★ recommended

DDD basics (bounded contexts overview) ★ recommended

API design: idempotency & contracts ★ recommended

Background jobs design ★ recommended

Migration strategy for schema changes ★ recommended

Query optimization and N+1 avoidance ★ recommended

Caching patterns (read-through, write-through) ★ recommended

Load testing basics (overview) ★ recommended

Connection pooling (overview) ★ recommended

Profiling and bottleneck hunting ★ recommended

Horizontal scaling basics ★ recommended

Queues, retries, dead-letter (overview) ★ recommended

Event-driven concepts (overview) ★ recommended

Consistency: eventual consistency basics ★ recommended

Multi-tenant considerations (overview) ★ recommended

Timeouts, circuit breakers (overview) ★ recommended

Graceful degradation strategy ★ recommended

Disaster recovery plan basics ★ recommended

Audit logs and traceability ★ recommended

Security hardening checklist (overview) ★ recommended

Metrics vs logs vs traces (overview) ★ recommended

Error tracking and alerting basics ★ recommended

Dashboards for SLIs/SLOs (overview) ★ recommended

Incident response runbooks ★ recommended

Postmortems: process and template ★ recommended