Emissary-Ingress and Edge Stack are two different products from Ambassador that serve as an API Gateway. Both share similarities in being built on Envoy Proxy, but differ in their release schedules, maintenance, feature sets, and continued support. Edge Stack is a commercial product with regular updates and bug fixes, while Emissary-Ingress is an open-source project with limited release schedule and community-driven support. Edge Stack offers a wider range of features, including authentication, rate limiting, and web application firewall, whereas Emissary-Ingress provides circuit breakers, load balancing, and distributed tracing. Ultimately, if you need the most actively supported, feature-rich, scalable, and configurable API Gateway option, Edge Stack is recommended, with its support available on a 5 x 8 or 24 x 7 basis, depending on your needs.