Backend 0 → PRO

Layering: controllers/services/repositories

DDD basics (bounded contexts overview)

API design: idempotency & contracts

Background jobs design

Migration strategy for schema changes

Query optimization and N+1 avoidance

Caching patterns (read-through, write-through)

Load testing basics (overview)

Connection pooling (overview)

Profiling and bottleneck hunting

Horizontal scaling basics

Queues, retries, dead-letter (overview)

Event-driven concepts (overview)

Consistency: eventual consistency basics

Multi-tenant considerations (overview)

Timeouts, circuit breakers (overview)

Graceful degradation strategy

Disaster recovery plan basics

Audit logs and traceability

Security hardening checklist (overview)

Metrics vs logs vs traces (overview)

Error tracking and alerting basics

Dashboards for SLIs/SLOs (overview)

Incident response runbooks

Postmortems: process and template