Making Shopify’s Flagship App 20% Faster in 6 Weeks Using a Novel Caching Solution
Article Summary
Shopify's home feed was consuming 30% of their total database load and slowing down their entire app. Off-the-shelf caching solutions wouldn't cut it.
The Shop app serves tens of millions of users tracking orders from checkout to delivery. The engineering team needed a caching solution that could handle concurrent updates to sorted lists without ever serving stale data to users.
Key Takeaways
- Built custom write-through cache using Memcached in just 6 weeks
- Reduced database load by 15% and app latency by 20%
- Used pending writes counter to handle concurrent updates safely
- Tested correctness for weeks before rollout by comparing cache vs database
- Integrated seamlessly via Active Record Concerns with zero API changes
Critical Insight
A custom caching solution delivered 20% faster performance and 15% lower database load in 6 weeks, proving that building your own infrastructure can beat off-the-shelf tools when requirements are unique.
