Enhancing Expensify app performance

Expensify was preparing a major app upgrade—not just in features, but in performance. The new version needed to feel fast and responsive across all platforms without sacrificing functionality.

The key challenge was to drastically reduce delays in core interactions, particularly in areas like messaging and screen transitions, while maintaining app stability and feature parity across mobile, web, and desktop environments.

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To guide the optimization process, we used the DMAIC framework—a structured, iterative approach for identifying, measuring, and improving performance. This allowed us to focus efforts on the areas with the highest impact.

Define

We aligned on business priorities and technical KPIs, focusing on message send time, app launch speed, and screen load performance.

Measure

Using tools like DevTools, Bun, Maestro, and real-device testing, we captured detailed benchmarks across environments to identify bottlenecks.

Analyze

We investigated memory usage, CPU strain, and render cycles to isolate performance-critical code paths and inefficient rendering patterns.

Improve

Targeted improvements were rolled out through iterative cycles, each backed by validation benchmarks. We focused on code efficiency, bundling, navigation, and UI rendering paths.

Control

To protect results long term, we integrated Reassure into the CI pipeline—allowing for real-time regression detection and continuous performance tracking.

Expensify now has a significantly faster app across platforms, particularly in message handling and screen rendering. End-users experience smoother transitions and reduced latency, especially in performance-sensitive areas.

In parallel, continuous monitoring infrastructure ensures these gains are preserved over time.

Expensify project is available in the Open Source for everyone to see. You can visit it and check the results of our work yourself.