API Security Best Practices Every Developer Must Know

APIs are the most common attack surface in modern web applications, and the OWASP API Security Top 10 reads like a checklist of mistakes we see in code reviews every week. In our API development practice, security is not a phase at the end of the project—it is a set of patterns baked into every endpoint from day one. This guide covers the five vulnerabilities that cause the most real-world damage and exactly how to prevent them in Node.js and Python backends.

Broken Object Level Authorization (BOLA), formerly known as IDOR, is the most prevalent API vulnerability. It occurs when an endpoint uses user-supplied IDs to access resources without verifying the requesting user owns or has access to that resource. The fix is a single pattern: always filter database queries by the authenticated user's ID, never by a raw parameter. Rate limiting is the second most-ignored protection—without it, your authentication endpoints are trivially brute-forceable and your scraping surface is open. Implement token bucket rate limiting at the infrastructure level (Nginx, API Gateway) and at the application level for sensitive routes. For our custom software clients, we use a layered approach: IP-level limits at the edge, user-level limits in Redis, and endpoint-specific limits for auth flows. Input validation, proper JWT handling with short expiry and refresh token rotation, and secrets management via environment variables rather than hardcoded values complete the foundational security posture that every API serving a mobile app or web application must have.