Security concepts every backend developer should know 👀

Security concepts every backend developer should know 👀 Webhook Verification If you accept webhooks from services like Stripe or Paystack, always verify the signature. Without verification, anyone can fake events and trigger sensitive actions in your system. That's how fake payment confirmations happen. SQL Injection This happens when user input is inserted directly into database queries. An attacker can manipulate that input to read, modify, or delete data they shouldn't have access to. Parameterized queries and ORMs exist for a reason. Use them. Input Validation Never trust client input. Even if your frontend validates data, attackers can bypass it completely and hit your API directly. Every backend should validate data at the server level before processing it. Password Hashing Passwords should never be stored as plain text. They should be hashed using strong algorithms like bcrypt or Argon2, so even if your database leaks, attackers can't instantly read user passwords. If you store raw passwords, a single breach becomes catastrophic. Rate Limiting Rate limiting controls how many requests a client can make within a time window. Without it, attackers can brute-force logins, spam endpoints, or overload your API. This is one of the simplest protections against abuse. CORS CORS controls which domains can access your backend from a browser. Misconfigured CORS can expose private APIs to untrusted origins. A lot of developers set * during development and forget to lock it down in production. API Keys vs JWTs API keys identify applications. JWTs identify users. Using one where the other should be used creates security gaps, especially in multi-user systems. Knowing the difference is fundamental in backend architecture.