JSFoo 2019

On component architecture, front-end engineering and Developer Experience (DX)


Building a High Performance Mobile-First Web App | A case study of Jabong PWA

Submitted by Upendra Dev Singh (@uds) on Saturday, 1 June 2019

Duration: 40 mins full talk Section: Full talk (40 mins) Technical level: Advanced

View proposal in schedule


Modern web applications are JavaScript heavy. JavaScript ecosystem is such that you get a lot of tools, libraries, and the framework for free. The cost of using a framework could be very high. During this talk, I will take the audience through the Jabong PWA implementation using preact. I will talk about how we applied the domain-driven design approach to make some important architecture decisions upfront to choose our technology stack e.g preact, preact-router, in-house state management container (similar to redux). I will also talk about performance optimizations techniques we have used to achieve a perfect Lighthouse Score “100”. WPT report is available here https://webpagetest.org/lighthouse.php?test=190527_5T_a65fb33950a68ca88897b4ea3ceb66a5


This talk will cover how we have reduced the JavaScript footprint drastically using preact and related libraries. Also, we will talk about the code-splitting in preact app that allowed us to render a fully interactive page with just 18kb of JavaScript less than react size.

These are some of the latest web and browser technologies we have implemented.

ZERO render blocking requests
Intersection Observer
Lazy load images using Intersection Observer
Replace onScroll with Intersection Observer
Preload critical requests
Hybrid rendering
RequestAnimationFrame for visual changes
Passive Listeners
Precache future routes with serviceworker
Route-based & Component-based Code Splitting
HTTP/2 - Server push and multiplexing
Preconnect third party domains
Maximize GPU usage
Using the latest image formats for different browsers Progressive jpeg and WebP
Network API & dpr-based Image delivery
Web Font optimization

Speaker bio

Director of Engineering at Myntra Jabong
“Using technology to build product that helps customers to make better buying decisions”





  • Zainab Bawa (@zainabbawa) Reviewer 2 months ago

    Thanks for the proposal, Upendra. Since ReactFoo is only about React, I am moving your proposal to JSFoo Bangalore for consideration, as it doesn’t fit the theme for ReactFoo.

    • Zainab Bawa (@zainabbawa) Reviewer 2 months ago

      I have moved your proposal here, Upendra.

      • Upendra Dev Singh (@uds) Proposer 2 months ago

        Sure, noted. Thank you for your time.

  • Zainab Bawa (@zainabbawa) Reviewer 11 days ago

    Thanks for the submission, Upendra. I have confirmed your talk, based on the reviews. One of the things we have to work towards is reducing the content since too much is being covered here. More, during the rehearsals.

Login with Twitter or Google to leave a comment