title: Multi-Protocol APIs
description: Serve REST, GraphQL, gRPC, and JSON-RPC from a single JustAPI application.

JustAPI supports four API protocols out of the box, all within a single application.

1. REST API (OpenAPI 3.1)

The default protocol. All route decorators generate OpenAPI 3.1 documentation automatically.

@app.get("/items/{item_id}")
def read_item(request, item_id: int):
    return {"item_id": item_id}

Interactive docs:

2. GraphQL

Mount a GraphQL endpoint with GraphiQL UI in one line:

app.graphql(path="/graphql")
# GraphiQL IDE at http://localhost:8000/graphql

GraphQL uses async-graphql under the hood, compiled to Rust native code.

3. gRPC / Protobuf

Define a Protobuf service and mount it:

from justapi import Schema


class RPCRequest(Schema):
    method: str
    params: dict


@app.post("/rpc", body_schema=RPCRequest)
def handle_rpc(request):
    data = request.json()
    return {"status": "OK", "method": data["method"]}

gRPC uses tonic and prost in the Rust runtime for high-performance binary serialization.

4. JSON-RPC 2.0

Standard JSON-RPC 2.0 endpoint:

from justapi import Schema


class JSONRPCRequest(Schema):
    jsonrpc: str = "2.0"
    method: str
    params: list | dict = []
    id: int | str = 1


@app.post("/jsonrpc", body_schema=JSONRPCRequest)
def handle_jsonrpc(request):
    req = request.json()
    if req["method"] == "ping":
        return {"jsonrpc": "2.0", "result": "pong", "id": req["id"]}

Protocol Comparison

Scaffolding with CLI

# Generate a project with your preferred protocol
justapi create my_api --api-type graphql
justapi create my_api --api-type grpc
justapi create my_api --api-type jsonrpc
justapi create my_api --api-type rest

See Also

• CLI Project Scaffolder — Generate multi-protocol projects
• JustAPIApp — graphql() method
• Streaming Output — SSE and streaming responses