Getting to Slack Faster with Incremental Boot
Article Summary
Slack was making 4.2 million users wait through loading screens every single day. Time to fix that.
Slack's engineering team tackled a classic web app performance problem: their desktop app loaded a complete team model on every boot, causing painful delays on large teams. This deep dive explains how they borrowed from their mobile playbook to cut load times dramatically.
Key Takeaways
- Content visible dropped from 7 seconds to under 5 seconds
- Saved users 49.5 days of waiting time every single day
- Two phase boot: show one channel first, load full model in parallel
- Parallelized work behind slow API calls for net performance win
- New metrics tracked content visible separately from fully loaded
Critical Insight
By loading incrementally instead of building a complete model upfront, Slack cut initial load time by 2+ seconds while also improving full load performance.
