The Expensify App Performance Makeover

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Callstack Cosmos
Callstack Cosmos


In brief

We optimized the client’s mobile app performance and introduced a custom tool to measure performance regressions. We set up performance tests and documentation to enable a seamless transition of knowledge with the in-house team of developers.

Client Info
Entain is one of the world’s largest sports betting and gaming entertainment groups.
Commercial gaming
Company type
Australia, Asia & Oceania
Tech Info
Performance optimization project with the best practices, approaches & tech solutions
React Native | Native
iOS | Android
Redux | Tanstack | Reassure | GraphQL

Performance Boost


In 87.5% of the screens, the number of rerenders decreased or remained the same, which affected the acceleration of the initial performance.

React Universe

In brief

Discover how we revamped the Expensify app for lightning-fast experiences, guided by a systematic DMAIC approach.

From 14.5 to 2.5 seconds

Sending a message took approx. 14.5 seconds on average. We reduced this baseline value to approx. 2.5 seconds.

reduced time of sending a message


Expensify was on the brink of a major app upgrade, aiming for not just a facelift but a complete performance overhaul. They needed speed, and they needed it to feel effortless.

The key challenge lay in optimizing performance without compromising functionality. Expensify's new app version demanded a level of responsiveness that would elevate user interactions to a seamless experience.

Approach & Work done

Adopting the DMAIC framework (Define, Measure, Analyze, Improve, Control), we approached the task systematically, ensuring each step contributed to the overarching goal of enhancing app performance.


We clearly defined objectives and metrics, aligning them with Expensify's business goals. Through collaborative discussions and analysis, we identified key performance indicators (KPIs) such as message sending time, and setting realistic targets to drive improvements.


With defined metrics in hand, we proceeded to measure baseline performance, leveraging a combination of tools and techniques such as DevTools component, Bun, and Maestro. Rigorous testing on various devices and environments allowed us to gather comprehensive data, showing performance bottlenecks.


Then, we delved into a detailed analysis of performance issues, with a special focus on factors impacting app responsiveness. From CPU profiling to memory utilization, we left no stone unturned in identifying root causes and preparing effective strategies for optimization with specific action items.


Thanks to our meticulous analysis, we knew exactly what to do - we started to implement targeted improvements. Through iterative development cycles and rigorous testing, we fine-tuned app performance, achieving significant reductions in message-sending times and enhancing overall responsiveness.


We didn’t stop there. To maintain optimal app performance over time, we integrated Reassure into Expensify's development pipeline. Continuous performance monitoring and identification of regressions let Expensify keep the great results.


With DMAIC guiding us, we gave Expensify's app a serious performance boost. Smooth chats, snappy responses - that's the Expensify experience, now better than ever. 

table with metrics showing before and after our work

Apart from all the fixes and improvements, we provided metrics that should be tracked over time so the client knows exactly what to monitor and correct to maintain great performance levels long term.

The challenges we’ve solved so far

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