Limit concurrent requests using a middleware

 DOS attacks are very popular and relatively easy to conduct. Implement rate limiting using an external service such as cloud load balancers, cloud firewalls, nginx, rate-limiter-flexible package or (for smaller and less critical apps) a rate limiting middleware (e.g. express-rate-limit)
Otherwise: An application could be subject to an attack resulting in a denial of service where real users receive a degraded or unavailable service.