---
title: "How Etsy gets its mobile apps ready for peak traffic"
description: "Mobile apps cannot be reverted after release, so Etsy’s peak traffic preparation focuses on observability and mitigation decisions made months in advance rather than capacity scaling during the event. The company runs a code slush with three phases: mindful merging in mid-October, infrastructure fortification, and peak requiring senior sign-off for any change. To avoid tooling disruption, Etsy ran both legacy and new crash reporters simultaneously through a dual-reporting layer, letting engineers use the tool they knew and providing comparison data to eventually sunset the old platform. Before peak, each crash-prone feature is ensured to have a remote flag that disables the failing code path without an app store release. Crash rate is translated into an estimate of lost orders via business analysts, making technical health discussable with teams and the CTO."
---

# How Etsy gets its mobile apps ready for peak traffic

[Sentry](https://yomu.fyi/company/sentry) · Sergiy Dybskiy · Sep 30, 2026

**Type:** Explainer

## Summary

Mobile apps cannot be reverted after release, so Etsy’s peak traffic preparation focuses on observability and mitigation decisions made months in advance rather than capacity scaling during the event. The company runs a code slush with three phases: mindful merging in mid-October, infrastructure fortification, and peak requiring senior sign-off for any change. To avoid tooling disruption, Etsy ran both legacy and new crash reporters simultaneously through a dual-reporting layer, letting engineers use the tool they knew and providing comparison data to eventually sunset the old platform. Before peak, each crash-prone feature is ensured to have a remote flag that disables the failing code path without an app store release. Crash rate is translated into an estimate of lost orders via business analysts, making technical health discussable with teams and the CTO.

## Context

Mobile apps cannot be reverted like web deployments, so peak traffic preparation must focus on observability and mitigation decisions made months in advance rather than capacity scaling during the event.

## Approach / What changed

Etsy uses a graduated code slush with three phases, dual crash reporters during vendor transitions, remote feature flags for all crash-prone code, strict alert reduction to two actionable metrics, and business-aligned crash cost estimation to justify observability investments.

## Takeaways

- Etsy runs a code slush with three phases (mindful merging, infrastructure fortification, peak requiring senior sign-off) to raise the shipping bar gradually before peak traffic instead of using a hard code freeze.
- To avoid disrupting engineers during the holidays, Etsy kept its legacy crash reporter running alongside a new Sentry integration through a dual-reporting layer so engineers could keep using the tool they already knew.
- Etsy translates crash rate into an estimated number of lost orders by working with business analysts, making technical health discussable with product teams in a currency the business already tracks.

## FAQ

### How does Etsy handle code changes during peak without a full freeze?

Etsy uses a code slush with three phases that raise the bar gradually from mid-October through peak, culminating in requiring very senior sign-off for any change during Cyber Week.

### What did Etsy do when migrating to a new crash reporter before peak?

Etsy set up a dual crash reporter that sent data to both the legacy platform and new Sentry integration simultaneously, letting engineers keep using the familiar tool and providing real-world comparison data to eventually justify sunsetting the old platform.

### How does Etsy calculate the business impact of crashes?

Etsy worked with business analysts to estimate lost orders by multiplying the number of users hitting a crash by the likelihood the crash prevented a purchase and by average order value, producing a rough number that makes crash rate discussable with product teams.

**Tags:** [Mobile](https://yomu.fyi/topic/mobile), [Observability](https://yomu.fyi/topic/observability), [Release Engineering](https://yomu.fyi/topic/release-engineering), [Sentry](https://yomu.fyi/topic/sentry)

- Source: [Sentry](https://blog.sentry.io/etsy-peak-traffic-prep)
- Source URL: https://blog.sentry.io/etsy-peak-traffic-prep
- Ingested by Yomu: 2026-09-30T18:00:12.142Z

[Read original post](https://blog.sentry.io/etsy-peak-traffic-prep)