Inside Slack: Overcoming Challenges to Craft a Seamless Mobile App

Slack's mobile team faces a unique challenge: users expect desktop-level performance while bouncing between subway tunnels and spotty cellular networks.

Tracy Stampfli, Principal Engineer on Slack's mobile infrastructure team, reveals how her 120+ person engineering org builds the backbone that keeps Slack running smoothly for millions of mobile users. This deep dive covers everything from handling intermittent connectivity to managing massive scale.

Key Takeaways

• API request prioritization ensures critical data loads first under poor connectivity
• Object versioning validates cached data freshness, dramatically reducing data usage
• Feature flagging and server-side toggles enable instant rollbacks without app updates
• Infrastructure supports extreme cases: 80,000 custom emoji and 20,000 channels per user
• Shared component library lets any feature work offline with automatic sync

The article reveals their specific versioning technique that cut data usage and how they prevent cascading failures across the entire app.