I believe what Overmind meant was that a single request in another language can probably beat Elixir in performance, but Elixirs ability to handle a large amount of requests concurrently means that it'll have better throughput.
For example, if a web request in framework A takes 100ms and framework B takes 200ms, but framework B can handle 4,000 requests concurrently and framework A can handle 1,000 requests concurrently, then framework B will beat framework A in handling 20,000 requests.
framework A - (20,000r / 1,000r) * 100ms = 2,000ms
framework B - (20,000r / 4,000r) * 200ms = 1,000ms
For example, if a web request in framework A takes 100ms and framework B takes 200ms, but framework B can handle 4,000 requests concurrently and framework A can handle 1,000 requests concurrently, then framework B will beat framework A in handling 20,000 requests.
framework A - (20,000r / 1,000r) * 100ms = 2,000ms
framework B - (20,000r / 4,000r) * 200ms = 1,000ms