Building an OG Scraping Server in Node.js (1): From Runtime Choice to Error Rate and Latency

The "10% error rate" of a link preview server is a single number that five different kinds of failure got mashed into. This post works out why this workload is I/O bound at that TPS, where runtime choice actually diverges across four points, and then moves on to lowering the error rate with User-Agent and encoding. Node built-in TextDecoder turns CP949 extension characters into different characters without raising an error, and a scraped og:title is not an API response but user input. It also covers cache stampedes, negative caching, and a two-million-run simulation that verifies "P95 under one second" by working backwards from the cache hit rate. The first post of a two-part design note on OG scraping servers.