Just a digital ocean droplet running FreeBSD, then PM2 running Node.JS and ImageMagick built with multicore support.
One wonders if you can WASM-ify ImageMagick and the use a JS FileReader and a canvas or other PNG output approach to do this all client side. Hrmm, I might tackle this myself if I get the time...
Looks like someone has gotten pretty far WASM-ifying ImageMagick already [1]!
ImageMagick with "multicore" support won't speed things up the moment number of concurrent requests touches the number of cores you have. And in digital ocean's case you have only one core.
Actually I created a Droplet with 6 cores
But remember that multi-threading was shown to improve performance in the era of single-core computers.
Sure, but if your concurrent number of fully tendered requests at least sometimes dips below the number of cores, it is a big win.
(At the possible cost of top-end scale; improving response to normal workload significantly and hurting the top workload reachable somewhat).