Frontend Engineer II, IES Latency

About Us
The IES Latency team owns Lightsaber — a progressive and proximal rendering framework that makes Amazon pages load faster by serving content locally from the customer's device while fetching dynamic content from the server in parallel.
Lightsaber has made Android mShop faster than iOS on key shopping pages — a result that defies conventional expectations and demonstrates the power of software-driven latency optimization over hardware advantages. We operate across the
full stack — from Service Workers running in the browser to backend services behind Shopping Portal — optimizing latency for hundreds of millions of shoppers on mShop (Android & iOS), mobile web, and desktop across all Amazon marketplaces
worldwide. In 2026, our focus is bringing these same capabilities to iOS to close the gap, while continuing to push Android latency even lower.
Key job responsibilities
Technical Areas
- mShop Android app: Service Workers, Cache Storage API, page shell caching, prefetching, skeleton loaders, rendering hints, TRIMs transitions
- mShop iOS app: Rendering hints, skeleton experiences, deeplink latency optimization via JumpStart
- Client-side performance: TypeScript, streaming response composition, browser rendering pipeline, perceived latency techniques
- Backend services: Java, Spring, Horizonte, ECS Fargate, NLB, BigMesh, Shopping Portal integration
- Experimentation: Weblab design, triggering strategies, latency metric analysis, business impact measurement across 20+ marketplaces
- Operational excellence: Owning and operating two Tier-1 services (Lightsaber and AUIServiceWorkerService), CloudWatch, RTLA, CI/CD pipelines, chaos testing, autoscaling, cross-AZ load balancing, Zonal Shift
A day in the life
What You'll Work On
- Lightsaber's core client engine — page shell caching, prefetching, skeleton loaders, and rendering hints that reduce page load times by 50-120ms on core shopping pages (Detail Page, Search, Checkout, Homepage, Cart)
- TRIMs (Trust Reinforcing Microinteractions) — perceived latency experiences using motion and visual feedback during page transitions to improve checkout conversion
- Launching Lightsaber on iOS mShop — bringing rendering hints and skeleton experiences to iOS, closing the latency gap where iOS DP latency (1071ms) significantly lags Android (815ms)
- AUIServiceWorkerService — a Horizonte/Spring backend service running on ECS behind Shopping Portal that serves service worker scripts and CSRF tokens to millions of concurrent users
- Collaborating with partner teams across Shopping Portal, Detail Page, Search, Checkout, Cart, Homepage, Mobile Shopping Foundations, and AUI to design, experiment, and launch latency optimizations across the shopping funnel
Impact
- Your work directly reduces page load times for 500M+ shoppers across every Amazon marketplace
- TRIMs targets +$40MM OPS and +$80MM cumulative CSales through improved perceived performance
- You'll own the full lifecycle — from design and experimentation to production launch and operational health of Tier-1 services
- 2+ years of non-internship professional front end, web or mobile software development using JavaScript, HTML and CSS experience
- 1+ years of computer science fundamentals (object-oriented design, data structures, algorithm design, problem solving and complexity analysis) experience
- Experience using JavaScript frameworks such as angular and react
- 1+ years of agile software development methodology experience
- Experience with common front-end technologies such as HTML, CSS, JS, TypeScript, and Node
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