Scaling at Large - Lessons learned rewriting Instagram’s feed
summary
Instagram rewrites its iOS feed by replacing a single large “feed item” god object and massive view controllers with modular section controller modules, a linear-time diffing implementation based on Paul Heckel’s LCS, and an adapter that applies updates on the main thread. The open source project IGListKit (Objective‑C with some C++) provides diffing, adapters, working‑range prefetching, embedded lists, extensive unit and performance tests, and reports roughly 5.7 million diffs and batch updates run in production.
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