Express 5 on µWebSockets: same middleware, 2x to 7x
I maintain Fulmine , a drop-in replacement for Express 5 that runs on µWebSockets.js instead of node:http . One line changes: const express = require ( " fulmine.js " ); // instead of require("express") Your middleware keeps working: helmet , cors , passport , morgan , multer , express-session and the rest. The numbers are not mine Benchmarks published by a project about itself deserve suspicion, so let me use somebody else's. HttpArena runs every framework on the same 64-core machine, in containers, under the same rules, and publishes the results. Express and Fastify are on that board too. Requests per second, from their published runs: Profile Fulmine Express Fastify Baseline (query parsing) 1,220,308 607,777 711,263 JSON (dataset + serialization) 1,111,187 395,361 522,201 Short-lived connections 1,026,789 278,163 298,779 Pipelined 7,259,814 1,009,543 1,671,338 Mixed API workload, 16 CPUs 126,282 67,724 75,633 Async Postgres 222,701 169,687 179,169 Upload (20 MB body) 2,154 2,104 1,902 That is 2.0x Express on the baseline, 2.8x on JSON, 3.7x on short-lived connections, 7.2x pipelined , and 1.9x on the mixed API profile. Against Fastify, on the same board, it is 1.7x on the baseline and 2.1x on JSON. Now the honest parts, which matter as much as the table. Look at the upload row: 1.02x. A 20 MB body is memory bandwidth and syscalls, not framework code. Everywhere the cost belongs to a library both servers call, the difference disappears: JSON.parse , zlib, OpenSSL. Speed comes from the framework only where the framework is doing the work. My entry runs in the arena's "tuned" mode, Express's and Fastify's run in "standard". On two profiles I left out of the table, static files and compressed JSON, that difference is decisive, because tuned mode allows hand-written compression and negotiation. Those rows would show 23x and 8x, and they would be measuring my entry's tuning, not the framework. I would rather not quote them. Where the speed comes from Not from one trick