BackendDevelopment

You can write a CLI program that reads a file, processes data (filter, sort, transform), and outputs results. You can explain what happens when you type a URL and hit Enter.

You can build a fully functioning REST API with multiple routes, proper HTTP semantics, input validation, and structured error responses - testable via Postman or curl.

You can design a normalized relational schema, write complex JOINs and aggregations, set up indexes, and connect a live PostgreSQL database to your API using an ORM with migrations.

You can build a complete auth system with registration, login, JWT refresh flow, RBAC middleware, and resist common OWASP attacks in your API.

You can layer Redis caching onto an existing API, build a background job queue that handles email/image processing, and measurably reduce your API response time by 70% or more.

Your app lives in Docker, deploys automatically via GitHub Actions on every merge to main, runs on a cloud VPS with SSL, and has a managed PostgreSQL plus Redis setup.

Your APIs have 80%+ test coverage, structured logs flowing to a log aggregator, Sentry capturing exceptions, and a Grafana dashboard showing request rates, errors, and latencies.

You can confidently whiteboard a scalable system for any common design interview question, justify your trade-offs, and identify bottlenecks in an existing architecture.