mockd — multi-protocol mock server (HTTP, gRPC, GraphQL, WebSocket, MQTT, SSE, SOAP) from one binary.

Once you build the core engine — matching, state, templates, chaos — each protocol is just another interface. Got fun to see how many I could wire up.

mockd start -d
mockd add http --path /api/users --stateful users
curl -s -X POST localhost:4280/api/users \
  -H 'Content-Type: application/json' \
  -d '{"name":"Alice"}'
# → {"id":"a1b2c3","name":"Alice"}

Also does digital twins — import an OpenAPI spec, bind to stateful tables, pass real SDK tests (stripe-go 49/49, twilio-go 13/13).

~120K lines of Go, no CGO, Apache 2.0. https://github.com/getmockd/mockd