API Authentication Methods Compared: JWT, OAuth, mTLS, and API Keys
There Is No Universal Best
API keys, JWTs, OAuth, mutual TLS, each authentication method fits some situations and not others. The right choice depends on who your callers are and what you're protecting.
Comparing them honestly means matching method to context, not crowning a single winner.
API Keys: Simple and Limited
API keys are the easiest to issue and use, which is exactly why they're everywhere. They identify a caller but carry no expiry or fine-grained scope by default, so they suit low-risk, server-to-server use.
They're a fine starting point, but a long-lived key in the wrong place is a standing liability. Rotate them and keep them out of client code.
JWTs: Stateless and Scoped
JSON Web Tokens carry claims and scopes in a signed, short-lived package, letting services verify a caller without a database lookup. That statelessness is powerful and also the main pitfall, since a leaked token is valid until it expires.
Keep lifetimes short and scopes narrow, and JWTs give you fast, self-contained authorization.
OAuth and mTLS: When Stakes Are High
OAuth shines for delegated access on behalf of users; mutual TLS fits high-trust service-to-service links where both sides prove identity. Both cost more to operate and earn it when the risk justifies it.
Aurus supports these methods at the gateway, so teams can choose the right one per use case without building each from scratch.
