How do you handle a route where the param can be either a numeric ID or the literal string 'me' in NestJS?

Q: How do you handle a route where the param can be either a numeric ID or the literal string 'me' in NestJS?

@Controller('users') export class UsersController { // Must come BEFORE :id — declared first = matched first on Express @Get('me') getMe(@CurrentUser() user: User) { return user; } // Catches all other values including numeric IDs @Get(':id') findOne(@Param('id', ParseIntPipe) id: number) { return this.usersService.findOne(id); } } // GET /users/me -> getMe() handler // GET /users/42 -> findOne() handler with id = 42 // GET /users/abc -> findOne() handler — ParseIntPipe throws 400 Express matches routes in the order they are declared — specific literals must come first. Fastify uses a radix tree that automatically prefers static segments over parametric ones. Always declare literal routes before wildcard param routes regardless of platform — it is the safer convention. ParseIntPipe throws BadRequestException if a non-numeric value reaches the :id handler. This pattern extends to any reserved path segment like 'search', 'export', or 'count'.

Difficulty: 5/10

routing, parameter validation, custom pipes

Declare the specific literal route before the wildcard param route. On Express, NestJS matches routes in declaration order so GET /users/me matches the @Get('me') handler first. On Fastify a radix tree automatically prefers static routes, but declaring specific routes first is safer on both platforms.

Literal route before wildcard param route

Ordering rules for literal vs param routes:

1
Express matches routes in the order they are declared — specific literals must come first.
2
Fastify uses a radix tree that automatically prefers static segments over parametric ones.
3
Always declare literal routes before wildcard param routes regardless of platform — it is the safer convention.
4
ParseIntPipe throws BadRequestException if a non-numeric value reaches the :id handler.
5
This pattern extends to any reserved path segment like 'search', 'export', or 'count'.

Scenario Questions

0-2 years experience

1We have a GET /users/:id endpoint where :id can be a number or the string 'me'. How would you define the route and extract the parameter in NestJS?
2If you apply the built‑in ParseIntPipe to that route and a client calls /users/me, what will happen and why?
3Write a minimal custom pipe that accepts either a numeric ID or the literal 'me' and returns a consistent object for the controller.

Follow-up Questions

What edge cases might break your implementation?
How would you unit‑test the pipe or regex handling?
If you needed to add more special literals later, how would you extend the solution?