Kong since 0.x versions. We run into scale issues (database tuning parameters, caching, database replication) so I agree it would need a small team owning it. We actually use so little of the features that we consider building our own or look for other solutions.

https://www.haproxy.com/user-spotlight-series/building-a-glo... use haproxy as gateway. Possible because it's a single service, relatively simple authentication and users are fine without custom error responses. That might be worth looking into.