api gateway versus direct service calls what's the tradeoff

hey everyone, i'm trying to get a clearer picture on api gateways versus having frontend clients call microservices directly. i get that gateways can handle auth, rate limiting, and request aggregation, but does that complexity always outweigh the benefits? when have you found direct calls to be a better fit, or conversely, when was the gateway absolutely essential? curious about your experiences and the specific scenarios where each approach shines.