[Your Name] · [Email] · [Phone] · [City, ST]
April 21, 2026
Dear Hiring Manager,
I'm applying for the Senior iOS Engineer role on your Consumer App team. The teardown your engineering team published on your SwiftUI + TCA migration — and the honesty about where TCA didn't pay off — matched my experience almost exactly at Duolingo last year, and I'd love to work with a team that's willing to say that publicly.
At Duolingo I owned the iOS app performance workstream for the Streak feature — the highest-retention surface in the app. I rewrote the streak-calendar view from UIKit collection view to SwiftUI with LazyVGrid, cut cold-start time from 1.8s to 610ms on iPhone 12, and reduced main-thread jank from 14% of frames to 0.3% during the daily 6pm retention peak. That work shipped to 82M monthly active iOS users and moved 7-day retention 2.1 percentage points — a number I spent a month defending against seasonality skeptics before it was accepted. I also wrote the internal playbook on using Xcode Instruments to diagnose SwiftUI diff cycles, which is now the onboarding doc for our 14-person iOS team.
Before Duolingo I was the second iOS hire at a consumer fintech (Cash App Investing) where I shipped the first version of the portfolio view, built the custom charting library in Metal when performance fell short of UIKit's drawing, and owned the App Store release process through eight point releases. That end-to-end exposure — from Metal shader debugging to App Store Connect war rooms — is what I'd bring here. Your commitment to shipping native iOS instead of going cross-platform is one of the main reasons I'm applying; I think the craft difference still matters at consumer scale.
I'd welcome the chance to walk through the SwiftUI performance rewrite and hear where your team is on the TCA migration follow-through. I can share a redacted Instruments trace or jump on a call whenever fits your schedule.
Sincerely,
[Your Name]