Common Mistakes in Backend Assignment Submissions (and How to Fix Them?)
When submitting a backend assignment for a job interview, it’s easy to overlook critical details. These mistakes can make the difference between standing out as a strong candidate or getting rejected outright. Below are the most common pitfalls and how to avoid them:
1. Poor API Design
Why It’s a Problem:
Unstructured or inconsistent endpoints make the API difficult to use.
Using incorrect HTTP methods (e.g., GET for creating resources).
Not following RESTful or API best practices.
How to Fix It:
✅ Follow REST or GraphQL best practices.
✅ Use proper HTTP status codes (e.g., 201 for created, 400 for bad requests).
✅ Maintain consistency in endpoint naming (/users/{id} instead of /getUser).
2. Inefficient Database Queries
Why It’s a Problem:
Running unoptimized queries can slow down performance.
Missing indexes lead to slow lookups.
Using
SELECT *unnecessarily loads data.
How to Fix It:
✅ Optimize queries by selecting only required fields.
✅ Use indexing where necessary.
✅ Profile queries using EXPLAIN to detect bottlenecks.
3. No Pagination or Rate Limiting
Why It’s a Problem:
Fetching all records at once leads to performance issues.
APIs can get overwhelmed by too many requests.
How to Fix It:
✅ Implement pagination for large datasets (?page=1&limit=20).
✅ Use rate limiting to prevent API abuse (e.g., 100 requests per minute per user).
4. Hardcoded Secrets and Credentials
Why It’s a Problem:
Storing API keys, database credentials, or JWT secrets in code is a security risk.
Anyone with access to the repository can misuse them.
How to Fix It:
✅ Use environment variables (.env files) instead of hardcoded secrets.
✅ Add .env files to .gitignore to prevent accidental commits.
✅ Use secret management tools like AWS Secrets Manager or Vault.
5. Missing Error Handling
Why It’s a Problem:
Unexpected crashes due to unhandled errors.
Generic error messages make debugging difficult.
How to Fix It:
✅ Use structured error handling (try-catch or middleware in Express/Django).
✅ Return meaningful error messages with relevant HTTP status codes.
✅ Log errors properly for debugging.
6. Weak Security Practices
Why It’s a Problem:
APIs without authentication or authorization expose sensitive data.
Missing input validation leads to security vulnerabilities (SQL injection, XSS).
How to Fix It:
✅ Use authentication (JWT, OAuth, API keys) and enforce role-based access control.
✅ Validate and sanitize user inputs.
✅ Enable CORS properly to prevent unauthorized access.
7. Lack of Logging and Monitoring
Why It’s a Problem:
No way to debug production issues.
Difficulty in tracking user actions.
How to Fix It:
✅ Use logging libraries (winston, loguru, log4j).
✅ Implement structured logging with relevant metadata.
✅ Set up monitoring tools (Datadog, New Relic, Prometheus).
8. Poorly Structured Code
Why It’s a Problem:
Difficult to maintain and scale.
Mixed concerns (e.g., database queries inside controllers).
How to Fix It:
✅ Follow MVC or a clean architecture pattern.
✅ Separate concerns: Controllers handle logic, Services handle business rules, Repositories handle database queries.
✅ Use consistent naming conventions.
9. Not Writing Tests
Why It’s a Problem:
No way to verify that code changes don’t break functionality.
Harder to refactor confidently.
How to Fix It:
✅ Write unit tests for core business logic.
✅ Implement integration tests for APIs.
✅ Use testing frameworks (Jest, Mocha, PyTest, JUnit).
10. Ignoring Deployment Readiness
Why It’s a Problem:
Works locally but fails on a server.
Environment configurations are inconsistent.
How to Fix It:
✅ Use Docker or containerization to ensure consistency across environments.
✅ Document setup steps in a README.md.
✅ Test in a staging environment before final submission.
Final Checklist Before Submitting Your Backend Assignment
✅ Are all API endpoints well-structured and documented?
✅ Are database queries optimized?
✅ Have you implemented authentication and security best practices?
✅ Is error handling and logging in place?
✅ Did you write at least basic tests?
✅ Is your code well-structured and maintainable?
✅ Did you check your .gitignore to avoid committing secrets?
✅ Does your project run successfully in a clean environment?
Conclusion
Your backend assignment is not just about making things “work”. It’s about showing that you understand best practices, scalability, and security. Avoiding these common mistakes will help you stand out and demonstrate that you’re ready for real-world backend development.