API Security Hardening: JWT, Rate Limits, Tenant Isolation

Harden a Node API the defensive way: validate JWTs properly, fail safely, rate-limit abuse, and enforce tenant isolation so one customer can never read another's data.

Most API breaches aren't exotic — they're a token checked too loosely or a query missing a tenant filter. Here we harden a small Node/TypeScript API step by step: verify JWTs with issuer and audience, reject failures without leaking why, rate-limit to blunt abuse, and thread a tenant id through to the data layer so one customer can never see another's. Each step is one small change with a note on the attack it closes.

What you'll build

• Validate JWT signature, issuer, audience and expiry
• Authenticate requests with middleware and fail safely
• Rate-limit to blunt brute-force and abuse
• Enforce tenant isolation down to the query

Contents

1. An empty Node API
2. An endpoint worth protecting
3. Run it
4. Verify the signature
5. Check who issued it, and for whom
6. Authentication middleware
7. Fail safely
8. Lock the endpoint
9. Rate limiting
10. Apply the limit
11. Establish the tenant
12. Filter at the data layer
13. Wire isolation end to end