All 30 days
Day 28 / 30 · 2025 Edition
Performance at Scale
Measuring and testing performance, production monitoring, performance budgets, device tiers and optimizing for users in different regions.
Inside this day
Questions and detailed answers at four levels — Junior, Mid, Senior and Architect — with code samples and architect's insights.
Try answering each question out loud before you read the answer — that's the closest thing to a real interview.