Putting It All Together

You've built every layer:

Production JWT library checklist:

• Pin algorithms per-key (don't trust header alg)
• Constant-time signature comparison
• 32+ byte random keys for HS256
• Short exp (5-60 min); use refresh tokens for longer sessions
• Validate iss, aud, nbf, exp, optional nbf/leeway
• Support JWKS endpoints with kid for key rotation
• Cache JWKS responses (e.g. 1 hour) but refresh on unknown kid
• Don't put secrets in payload — anyone can read it
• Don't log full JWTs (token bearer)

What we glossed over:

• JWE (JSON Web Encryption): encrypted payload. RFC 7516. Used when payload IS sensitive.
• JWS detached payload: signature is separate from data. Useful for streaming.
• EdDSA / Ed25519: modern signing — faster and smaller than RSA, deterministic, no nonce-reuse footguns.
• PASETO / Biscuit: alternatives designed to fix JWT's footguns by removing dangerous features.

You now understand JWT well enough to use it (or argue against it). Many shops are moving to opaque tokens + Redis sessions because JWT's revocation story is ugly.