Software Engineer in E-commerce: Reducing Web Load Times
Evaluate frontend web performance bottlenecks to recover dropping mobile conversion rates on an e-commerce platform.
Context
You are a Frontend Software Engineer at an e-commerce platform. Three weeks ago, the team deployed a revamped checkout and product listing interface built with modern component libraries. Since the release, mobile web conversion has declined by 18%, and customer support tickets reporting unresponsive screens have surged. The engineering manager suspects slow backend APIs are the culprit and wants to spend the next sprint refactoring backend endpoints. You have 30 minutes to review the telemetry data, diagnose the true bottleneck, and deliver an action plan for the Head of Engineering.
Your Task
Present your technical assessment and resolution plan for the Head of Engineering formatted in three parts:
- Recommendation
- Impact
- Implementation Plan
Available Data
Core Web Vitals & Traffic Metrics (Mobile Web)
| Metric | Baseline (Pre-Release) | Current (Post-Release) | Target Benchmark |
|---|---|---|---|
| Mobile Conversion Rate | 2.8% | 2.3% | > 2.7% |
| Largest Contentful Paint (LCP) | 2.1s | 5.8s | < 2.5s |
| Total Blocking Time (TBT) | 180ms | 1,420ms | < 200ms |
| Cumulative Layout Shift (CLS) | 0.04 | 0.28 | < 0.10 |
| Average Backend API Latency | 210ms | 225ms | < 250ms |
| Initial JS Bundle Size (gzipped) | 340 KB | 1.45 MB | < 400 KB |
Telemetry indicates that while server API response times increased by only 15ms, client-side JavaScript execution time on mid-tier mobile devices jumped from 1.2 seconds to 4.9 seconds, primarily during initial hydration and checkout interactions.