Dedupe Middleware

Learn how to use context to prevent the same middleware from repeating expensive work when it runs multiple times in a single call.

Problem

The same middleware can run more than once during a single call. This often happens when:

• a procedure calls another procedure that both use the same middleware
• you use .use(authProvider).router(router), and some procedures in router already use authProvider

Solution

Store the computed value in context and reuse it when the middleware runs again.

For example, this middleware loads auth at most once per call:

const 
const authProvider: DecoratedMiddleware<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, unknown, any, Record<never, never>>authProvider = const os: Builder<DefaultInitialContext & object, Record<never, never>>
The oRPC procedure builder. Chain methods like `.input`, `.use`, and `.handler`
to define procedures, then compose them into routers.
@see{@link https://orpc.dev/docs/procedure Procedure}os
  .
Builder<DefaultInitialContext & object, Record<never, never>>.$context<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
}>(): Builder<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, Record<never, never>>$context<{ headers: Headersheaders: Headers, 
auth?: {
    id: string;
} | undefinedauth?: { id: stringid: string } | undefined, authLoaded?: boolean | undefinedauthLoaded?: boolean | undefined }>()
  .
Builder<{ headers: Headers; auth?: { id: string; } | undefined; authLoaded?: boolean | undefined; } & object, Record<never, never>>.middleware<{
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, unknown, any>(middleware: Middleware<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, unknown, any, Record<never, never>>): DecoratedMiddleware<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, unknown, any, Record<never, never>>middleware(async ({ 
context: {
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & objectcontext, next: MiddlewareNext<any>
Invoke to continue the middleware chain.next }) => {
    // reuse the loaded auth value if it was already loaded
    const 
const auth: {
    id: string;
} | undefinedauth = 
context: {
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & objectcontext.authLoaded?: boolean | undefinedauthLoaded
      ? 
context: {
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & objectcontext.
auth?: {
    id: string;
} | undefinedauth
      : await 
function loadAuth(headers: Headers): Promise<{
    id: string;
} | undefined>loadAuth(
context: {
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & objectcontext.headers: Headersheaders)

    return 
next: MiddlewareNext
<{
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}>(options: {
    context: {
        auth: {
            id: string;
        } | undefined;
        authLoaded: boolean;
    };
}) => MiddlewareResult<{
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, any>
Invoke to continue the middleware chain.next({ 
context: {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}context: { 
auth: {
    id: string;
} | undefinedauth, authLoaded: booleanauthLoaded: true } })
  })

You can now apply authProvider multiple times without loading auth again:

const 
const base: Builder<{
    headers: Headers;
} & object, Record<never, never>>base = const os: Builder<DefaultInitialContext & object, Record<never, never>>
The oRPC procedure builder. Chain methods like `.input`, `.use`, and `.handler`
to define procedures, then compose them into routers.
@see{@link https://orpc.dev/docs/procedure Procedure}os.
Builder<DefaultInitialContext & object, Record<never, never>>.$context<{
    headers: Headers;
}>(): Builder<{
    headers: Headers;
} & object, Record<never, never>>$context<{ headers: Headersheaders: Headers }>()

const 
const foo: DecoratedProcedure<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, InitialInputSchema, Schema<string>, Record<never, never>, never>foo = 
const base: Builder<{
    headers: Headers;
} & object, Record<never, never>>base.
Builder<{ headers: Headers; } & object, Record<never, never>>.use<{
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, {
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, Record<never, never>>(middleware: Middleware<({
    headers: Headers;
} & object) | ({
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object), {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, unknown, unknown, Record<never, never>>): BuilderWithMiddlewares<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, Record<...>>use(
const authProvider: DecoratedMiddleware<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, unknown, any, Record<never, never>>authProvider).
BuilderWithMiddlewares<{ headers: Headers; } & object & Omit<{ headers: Headers; auth?: { id: string; } | undefined; authLoaded?: boolean | undefined; } & object, "headers">, { auth: { ...; } | undefined; authLoaded: boolean; }, Record<...>>['handler']<string>(handler: ProcedureHandler<Omit<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, "auth" | "authLoaded"> & {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, unknown, string, ORPCErrorConstructorMap<Record<never, never>>>): DecoratedProcedure<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, ... 4 more ..., never>handler(({ 
context: Omit<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, "auth" | "authLoaded"> & {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}context }) => 'Hello World')

const 
const bar: DecoratedProcedure<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, InitialInputSchema, Schema<string>, Record<never, never>, never>bar = 
const base: Builder<{
    headers: Headers;
} & object, Record<never, never>>base.
Builder<{ headers: Headers; } & object, Record<never, never>>.use<{
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, {
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, Record<never, never>>(middleware: Middleware<({
    headers: Headers;
} & object) | ({
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object), {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, unknown, unknown, Record<never, never>>): BuilderWithMiddlewares<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, Record<...>>use(
const authProvider: DecoratedMiddleware<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, unknown, any, Record<never, never>>authProvider).
BuilderWithMiddlewares<{ headers: Headers; } & object & Omit<{ headers: Headers; auth?: { id: string; } | undefined; authLoaded?: boolean | undefined; } & object, "headers">, { auth: { ...; } | undefined; authLoaded: boolean; }, Record<...>>['handler']<string>(handler: ProcedureHandler<Omit<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, "auth" | "authLoaded"> & {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, unknown, string, ORPCErrorConstructorMap<Record<never, never>>>): DecoratedProcedure<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, ... 4 more ..., never>handler(({ 
context: Omit<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, "auth" | "authLoaded"> & {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}context }) => {
  // Reuse the auth value that is already stored in context.
  return 
call<Omit<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, "auth" | "authLoaded"> & {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, InitialInputSchema, Schema<string>, Record<never, never>, never>(lazyableProcedure: Lazyable<Procedure<Omit<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, "auth" | "authLoaded"> & {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, ... 4 more ..., never>>, input: void, options: CallOptions<...>): PromiseWithError<...>
Quickly call a procedure without creating a client.
@example```ts
const output = await call(getting, 'input')
const output = await call(getting, 'input', { context: { db: 'postgres' } })
```@see{@link https://orpc.dev/docs/client/server-side#one-off-calls Server-Side Clients - One-Off Calls}call(
const foo: DecoratedProcedure<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, InitialInputSchema, Schema<string>, Record<never, never>, never>foo, var undefinedundefined, { 
context: Value<Promisable<Omit<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, "auth" | "authLoaded"> & {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}>, [clientContext: object]>context }) 
})

// Applying authProvider again does not load auth a second time.
const 
const router: {
    foo: Procedure<{
        headers: Headers;
    } & object & Omit<{
        headers: Headers;
        auth?: {
            id: string;
        } | undefined;
        authLoaded?: boolean | undefined;
    } & object, "headers">, {
        auth: {
            id: string;
        } | undefined;
        authLoaded: boolean;
    }, InitialInputSchema, Schema<string>, Record<never, never>, never>;
    bar: Procedure<{
        headers: Headers;
    } & object & Omit<{
        headers: Headers;
        auth?: {
            id: string;
        } | undefined;
        authLoaded?: boolean | undefined;
    } & object, "headers">, {
        auth: {
            id: string;
        } | undefined;
        authLoaded: boolean;
    }, InitialInputSchema, Schema<string>, Record<never, never>, never>;
}router = 
const base: Builder<{
    headers: Headers;
} & object, Record<never, never>>base
  .
Builder<{ headers: Headers; } & object, Record<never, never>>.use<{
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, {
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, Record<never, never>>(middleware: Middleware<({
    headers: Headers;
} & object) | ({
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object), {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, unknown, unknown, Record<never, never>>): BuilderWithMiddlewares<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, Record<...>>use(
const authProvider: DecoratedMiddleware<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, unknown, any, Record<never, never>>authProvider) 
  .
BuilderWithMiddlewares<{ headers: Headers; } & object & Omit<{ headers: Headers; auth?: { id: string; } | undefined; authLoaded?: boolean | undefined; } & object, "headers">, { auth: { ...; } | undefined; authLoaded: boolean; }, Record<...>>['use']<object, Omit<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, "auth" | "authLoaded"> & {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, Record<never, never>>(middleware: Middleware<Omit<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, "auth" | "authLoaded"> & {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, object, unknown, unknown, Record<...>>): BuilderWithMiddlewares<...>use(({ next: MiddlewareNext<unknown>
Invoke to continue the middleware chain.next }) => {
    // Additional middleware logic
    return 
next: MiddlewareNext
<object>(options?: {
    context?: object | undefined;
} | undefined) => MiddlewareResult<object, unknown>
Invoke to continue the middleware chain.next()
  })
  .
BuilderWithMiddlewares<{ headers: Headers; } & object & Omit<{ headers: Headers; auth?: { id: string; } | undefined; authLoaded?: boolean | undefined; } & object, "headers">, { auth: { ...; } | undefined; authLoaded: boolean; }, Record<...>>['router']<{
    foo: DecoratedProcedure<{
        headers: Headers;
    } & object & Omit<{
        headers: Headers;
        auth?: {
            id: string;
        } | undefined;
        authLoaded?: boolean | undefined;
    } & object, "headers">, {
        auth: {
            id: string;
        } | undefined;
        authLoaded: boolean;
    }, InitialInputSchema, Schema<string>, Record<never, never>, never>;
    bar: DecoratedProcedure<{
        headers: Headers;
    } & object & Omit<{
        headers: Headers;
        auth?: {
            id: string;
        } | undefined;
        authLoaded?: boolean | undefined;
    } & object, "headers">, {
        auth: {
            id: string;
        } | undefined;
        authLoaded: boolean;
    }, InitialInputSchema, Schema<...>, Record<...>, never>;
}>(router: {
    foo: DecoratedProcedure<{
        headers: Headers;
    } & object & Omit<{
        headers: Headers;
        auth?: {
            id: string;
        } | undefined;
        authLoaded?: boolean | undefined;
    } & object, "headers">, {
        auth: {
            id: string;
        } | undefined;
        authLoaded: boolean;
    }, InitialInputSchema, Schema<string>, Record<never, never>, never>;
    bar: DecoratedProcedure<{
        headers: Headers;
    } & object & Omit<{
        headers: Headers;
        auth?: {
            id: string;
        } | undefined;
        authLoaded?: boolean | undefined;
    } & object, "headers">, {
        auth: {
            id: string;
        } | undefined;
        authLoaded: boolean;
    }, InitialInputSchema, Schema<...>, Record<...>, never>;
}): {
    ...;
}router({
    
foo: DecoratedProcedure<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, InitialInputSchema, Schema<string>, Record<never, never>, never>foo,
    
bar: DecoratedProcedure<{
    headers: Headers;
} & object & Omit<{
    headers: Headers;
    auth?: {
        id: string;
    } | undefined;
    authLoaded?: boolean | undefined;
} & object, "headers">, {
    auth: {
        id: string;
    } | undefined;
    authLoaded: boolean;
}, InitialInputSchema, Schema<string>, Record<never, never>, never>bar,
  })