How one language-neutral spec runs 100+ machine-coding problems across four languages — runtime dispatch for Python, JavaScript, and Java, code generation for C++, and the thin output contract that makes adding a new language a one-file change.

A reconstruction of how LinkedIn's feed retrieval engine (FishDB) likely works — graph-anchored retrieval, scatter-gather over 48 shards, and the one-writer-per-shard rule that makes reads lock-free.