flutter-perf-derived-state

Use when the same values are recomputed on every rebuild or the client repeatedly scans thousands of records. Optimises derived and aggregated state in a Flutter app without changing results: totals, counts, percentages, balances, scores, grouped or sorted collections, and other values computed from large datasets. Covers memoisation, provider-level caching, incremental calculation, and deciding whether aggregation or pagination belongs on a backend instead of the client. Do not use to change calculation rules.