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Error Handling Architecture

Standardized error handling patterns across the API layer.

Global Exception Filter​

All unhandled exceptions are caught by the global exception filter:

@Catch()
export class AllExceptionsFilter implements ExceptionFilter {
  catch(exception: unknown, host: ArgumentsHost) {
    const ctx = host.switchToHttp();
    const response = ctx.getResponse<Response>();

    const status =
      exception instanceof HttpException
        ? exception.getStatus()
        : HttpStatus.INTERNAL_SERVER_ERROR;

    response.status(status).json({
      statusCode: status,
      message: this.getErrorMessage(exception),
      timestamp: new Date().toISOString(),
    });
  }
}

Standard Error Responses​

400 Bad Request​

Validation errors return field-level details:

{
  "statusCode": 400,
  "message": ["email must be an email", "name should not be empty"],
  "error": "Bad Request"
}

401 Unauthorized​

{
  "statusCode": 401,
  "message": "Unauthorized"
}

403 Forbidden​

Missing permissions:

{
  "statusCode": 403,
  "message": "You do not have permission to access this resource"
}

404 Not Found​

{
  "statusCode": 404,
  "message": "Record not found"
}

409 Conflict​

Duplicate records:

{
  "statusCode": 409,
  "message": "Email already in use"
}

429 Too Many Requests​

Rate limiting:

{
  "statusCode": 429,
  "message": "ThrottlerException: Too Many Requests"
}

Custom Exceptions​

// Usage in services
throw new NotFoundException("Employee not found");
throw new ForbiddenException("Insufficient permissions");
throw new ConflictException("Email already exists");
throw new BadRequestException("Invalid date range");

Error Logging​

All 5xx errors are logged with full stack traces. 4xx errors are logged at warn level.