How I built an in-memory explicit content filter in Node.js (200ms latency, zero images saved)

If you allow user-generated content in your app, you eventually run into a massive liability problem. Users will upload NSFW images. I ran into this exact problem when Apple rejected my previous app under Guideline 1.2 (User Generated Content). I needed a filter, but the standard way most tutorials teach you to handle this is flawed. Usually, the...