Question 1

Should I use OAuth 2.0, JWTs, or API keys?

Accepted Answer

They solve different problems and often coexist. OAuth 2.0 (with OpenID Connect for identity) is the standard for letting users or third parties grant scoped access without sharing passwords. JWTs are a token format often used inside OAuth for stateless, self-contained sessions. API keys suit simple service-to-service calls where a long-lived secret is acceptable. We map each to the right use rather than forcing one everywhere.

Question 2

Are JWTs safe to store in the browser?

Accepted Answer

It depends where. Storing tokens in localStorage exposes them to XSS, so for browser apps we prefer short-lived access tokens in memory plus a refresh token in an HttpOnly, Secure, SameSite cookie that JavaScript can't read. Keeping access-token lifetimes short — minutes, not days — limits the damage if one does leak. The right pattern depends on your app's threat model.

Question 3

What is BOLA and why does it matter?

Accepted Answer

Broken Object-Level Authorization (BOLA/IDOR) is the number-one risk on the OWASP API Top 10: an authenticated user requests an object ID that isn't theirs, and the API returns it because it only checked that they're logged in, not that they own the record. Every endpoint that takes an ID must verify ownership server-side. We test for this explicitly because it's both common and high-impact.

Question 4

How do I revoke a JWT before it expires?

Accepted Answer

Pure JWTs are stateless and can't be revoked directly, which is the trade-off for not hitting a database on every request. The practical fixes are short token lifetimes plus a refresh mechanism, a server-side denylist of revoked token IDs checked on sensitive actions, or token versioning tied to the user record. We choose based on how fast you need revocation to take effect.

Question 5

Should I build auth myself or use Auth0/Clerk?

Accepted Answer

For most teams a managed provider is the safer, faster choice — it handles MFA, social login, password resets, and security patches that are easy to get wrong. Self-hosting makes sense when you have strict data-residency rules, unusual flows, or want to avoid per-user pricing at large scale. We've shipped both and will recommend honestly based on your constraints.

Question 6

How do I secure machine-to-machine API calls?

Accepted Answer

Use the OAuth 2.0 client-credentials grant or signed, scoped API keys rather than embedding user credentials. Each service gets its own identity and least-privilege scopes, secrets live in a vault not in code, and keys are rotated regularly. Mutual TLS adds another layer for high-trust internal communication.

Question 7

How do you prevent token leakage and replay?

Accepted Answer

We transport everything over TLS, keep tokens out of URLs and logs, and use short lifetimes so a captured token expires quickly. For sensitive operations we add request signing and nonces so a replayed request is rejected. Refresh tokens are rotated on each use, so a stolen one is detectable the moment the legitimate client uses theirs.

Question 8

Does this cover compliance requirements?

Accepted Answer

Authentication and authorization are the foundation of most compliance regimes, but they're not the whole picture. Our audit logging, access controls, and encryption support GDPR, SOC 2, and similar frameworks, and we document the controls for your auditors. We'll flag where API security ends and broader organizational controls — policies, training, vendor management — must take over.

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