Tyk is an open-source API gateway written in Go that fronts REST, GraphQL, gRPC, and async (Kafka, SSE, WebSocket) APIs. The gateway handles the usual concerns: authentication, rate limiting and quotas, request and response transformation, versioning, circuit breaking, and analytics.
It supports most common auth schemes out of the box, including API keys, JWTs, OAuth2, OpenID Connect, HMAC, and mTLS, and policies are attached to keys so rate limits and access rights travel with the consumer. Custom logic can be added with middleware written in JavaScript, Python, Lua, gRPC plugins, or Go plugins compiled into the gateway. For GraphQL, Tyk can act as a universal data graph, stitching REST and gRPC upstreams into a single schema.
The gateway itself is open source under MPL-2.0, while the dashboard, developer portal, and multi-data-center management (“Tyk Cloud” / self-managed) are commercial. It is commonly deployed in front of internal APIs or as an alternative to Kong and Apigee.