A Summer of Android at Strava

Artem Sharypov from Strava's Experience team rebuilt their entire Android upload service from scratch. Why throw away working code? Because sometimes technical debt costs more than a rewrite.

During his 2019 summer internship, Artem tackled a critical infrastructure challenge: migrating Strava's Android activity uploads from JSON to FIT file format. The existing service worked, but its rigid architecture made it nearly impossible to support both formats simultaneously without introducing bugs.

Key Takeaways

• FIT files are smaller than JSON, reducing upload failures on poor connections
• New architecture uses TaskRunner pattern with RxJava for testable, format-agnostic uploads
• Separate upload queues and polling logic made old system impossible to debug
• Task-based design allows independent retry strategies for JSON and FIT uploads

The article reveals the specific architectural pattern that made testing the old service require 'hacky solutions' and how the new design eliminated that problem entirely.