A software engineer who worked on Instagram Reels recommendations at Meta shares how the team achieved megawatt-scale energy savings and eight-figure annual cost reductions by optimizing the data pipeline rather than the models themselves. Three key techniques were used: 'lazy logging' (only persisting feature vectors for the first few items a user is likely to see, then paginating on demand), batched storage schemas (storing user features once per request instead of duplicating them per impression, cutting storage by 40%), and large-scale feature auditing (removing thousands of statistically insignificant features to reduce inference latency and storage costs). The core insight is that efficiency in large-scale AI systems often comes from rethinking how data is computed, fetched, and stored rather than from model architecture changes.
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