Three Hidden Budgets That Quietly Kill Web App Performance

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A technical guide published on DEV Community outlines three critical performance constraints that every web application faces: browser bundle size, API rate limits, and database index selectivity. On the frontend, Lighthouse begins penalizing Time to Interactive once gzipped assets exceed 244 kB, and a simple import change — such as switching from full lodash to lodash/get — can reduce payload by up to 8x. API providers like GitHub, OpenAI, and Stripe enforce token-bucket rate limits that allow short bursts but throttle sustained overuse, returning 429 errors when exceeded. On the database side, indexes with low selectivity, such as a status column with only two values, are often ignored by the query planner, forcing full table scans across tens of thousands of rows. The guide provides formulas, threshold references, and a unified PR checklist covering frontend, backend, and database layers, along with four interactive calculators to help developers quantify each budget before merging code.

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