[Mobile Web] DoorDash's Lessons on Improving Performance on High-Traffic Web Pages

DoorDash users were waiting up to 10 seconds for pages to load. Here's how their team turned performance audits into measurable conversion wins.

Engineers Paipo Tang and David Nguyen share hard-won lessons from optimizing high-traffic web pages at scale. With 60+ engineers maintaining the codebase, they had to find quick wins that wouldn't break critical user flows.

Key Takeaways

• Upgrading one library eliminated 300KB and boosted conversions by 0.50%
• Lazy loading cut mobile First Input Delay by 67% (145ms to 48ms)
• Tree-shaking dependencies delivered the fastest performance ROI
• API response times were secretly blocking first paint for seconds
• Cache audits across CDN, HTTP, and app layers revealed hidden bottlenecks

The team reveals why some promising performance techniques turned into dead ends and which auditing tools actually caught the issues that mattered.