Company

Shopify

Every Shopify engineering case study on TechLogStack — real production incidents, post-mortems, and fixes.

Shopify Reliability
3 min

Shopify's Authentication Went Down on Cyber Monday — the Year's Biggest Shopping Day

At 6:45 AM Pacific on December 1, 2025, Shopify merchants started getting locked out of their own stores. The platform was in the middle of a record $14.6 billion holiday weekend.

Cyber Monday morning 4,000+ Downdetector reports $5.1M/min peak throughput +1 3.9% stock decline
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Shopify Databases
15 min

Shopify Sharded a Rails Database With Vitess and the App Never Knew It Happened

The Shop app was growing exponentially. Its single MySQL database was approaching vertical scaling limits. Shopify needed horizontal sharding — but they had a Rails monolith that expected a single database, and a system that couldn't have downtime during a commerce platform used by millions daily.

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Shopify Databases
15 min

Shopify's Engineers Hunted Deadlocks at 19 Million Queries per Second

During Black Friday and Cyber Monday 2023, Shopify's MySQL fleet was handling 19 million queries per second. At that scale, even rare deadlock patterns become common enough to cause real incidents. The engineering team published a detailed playbook for diagnosing and eliminating MySQL deadlocks in high-concurrency production environments.

19M MySQL QPS at BFCM peak 58M requests/min app servers 99.999%+ uptime maintained
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Shopify Reliability
19 min

The 80% Problem: Why Getting an LLM System to 'Works in Demo' Is 20% of the Work

Every team building with LLMs discovers the same brutal truth: 80% quality arrives in a few weeks. The final 15% — the gap between 'impressive demo' and 'product I'd trust with my customers' — takes the rest of the time. Shopify's Flow agent and Sidekick teams lived this curve and came back with a systematic playbook. It is mostly about measurement.

300-example hand-crafted benchmark
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