Backend Developer Career Guide: APIs, Databases and System Design Basics

The short version

Backend developers build the engine behind apps: logins, payments, search, notifications and data storage. If the idea of making things reliable and fast excites you, backend is your space.

What backend developers handle

• APIs that the web or mobile app calls
• Databases: designing tables and writing efficient queries
• Authentication and permissions
• Business rules, such as pricing or order flow
• Background jobs, queues and scheduled tasks
• Logging, monitoring and fixing production issues

Core skills

• One language well: Java, Python, JavaScript or TypeScript, C# or Go
• REST API design: resources, status codes, pagination and versioning
• SQL, indexes and transactions
• Caching basics and when to use it
• Authentication methods such as sessions and tokens
• Git, testing and deployment
• Docker and cloud basics as you grow

Design a small system: URL shortener

This classic exercise teaches you to think like a backend engineer.

1. List what it must do: create a short link, redirect to the long link, count clicks.
2. Design the data: a table with short code, long URL, created time and click count.
3. Define the APIs: create link, redirect, get statistics.
4. Decide how to generate unique codes and avoid collisions.
5. Think about speed: cache popular links, add an index on the code column.
6. Think about failure: what happens if the database is slow or down?

Roadmap

1. Learn one language and build simple command-line programs.
2. Learn SQL and design a small database.
3. Build a REST API with authentication.
4. Add tests and deploy it online.
5. Learn caching, queues and basic scaling ideas.
6. Read about system design and practise explaining designs aloud.

Interview questions

• What is the difference between SQL and NoSQL databases?
• What is an index and when can it hurt?
• How do you secure an API?
• What is idempotency and why does it matter for payments?
• How would you handle a sudden traffic spike?

Next step

Build the URL shortener this week. Then register on JobKarle and apply to backend roles.