Delayed experiments and bug fixes: The adoption time for newer app versions was very high, especially Android. It was ne

It’s true that optimised native apps can outperform React-Native versions most times. However, considering the benefits such as OTA updates, we came up with the success metric for this experiment.

We built internal infrastructure to diff JS and enable clients to download patches. We could drop our payloads size by over 90% for our weekly releases. This has become much better today and we’ve moved from ‘module-level diffs’ to ‘binary diffing’ using ‘bsdiff’.

To solve the infinite list problem, we had to build our own list view, which recycles cells instead of destroying and recreating to save memory and performance. Our first version was backed by native RecyclerView and UICollectionView, and in later revisions we built recyclerlistview in JS (only).

Reusing the React Instance Managers: We were building them again while switching between stacks. Rebuilding these managers requires a re-parse of JS, leading to slowdowns. You need to create and then cache in memory.

The ‘Home’ page being the first page did not present any chance to pre-run VMs unlike the rest of pages such as search, product, and videos. In instances such as Android App, the launch time was slower in React-Native as compared to the Native by almost 300–500ms (on Snapdragon 625). Therefore, to meet our metric goals, we kept our home page fully native.

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exposed, your child suffers. But if you are the source of that lie, they will suffer alone. They won’t reach out to you because you are the liar. And they may even piece together a narrative with a very cynical conclusion— no one can be trusted.

Every change in the app is profiled to analyse its impact on the core metrics. In our initial experiments with React-Native Android apps, the page load metrics were not as good as Native.

After the initial app launch for Android in 2016, we ran the same code on iOS. Code-sharing wasn’t very successful as some of the abstractions that we built for Android such as the listview was built on Android’s RecyclerView and proved difficult to implement on iOS.

A lot of teams get into conflicts between Native vs React-Native performance without setting targets. Our intent was to set targets and then see if React-Native can match it. The goal that we agreed internally was to go with React-Native, if we can maintain or do better than existing load time metrics and scroll FPS.

This revision in the thought process and discussion around deciding targets helped the entire team focus on the correct success metrics. After a few iterations, we could achieve the targets and React-Native became an obvious choice.

When we started, the efficiency in delivering JS updates OTA and improving the performance of the infinite list were our primary concerns. We needed some kind of bundle diffing to push frequent updates.

We read the source code and the comments on it, fixed memory leaks, and experimented with the possibilities in the usage of React-Native. Eventually, we saw success in migrating one of the most complex pages with no performance degradation.

In mid-2017, when we built Flipkart’s Grocery experience on the app, we carefully planned our code structure and native dependencies to avoid code sharing issues. We could share about 95% of the code in this exercise and the development was seamless as the native modules were reliable and reusable. This is when we also wrote the reyclerlistview to ensure a consistent, high-performant, and cross-platform list view (including web).

With Hermes being launched, we are repeating the same exercise to find out if we can move homepage to React-Native. We understand Hermes reduces the initial cost of parsing JS which helps with an improved launch performance.

Making a React instance available before the user loads the page (pre-run it). You can create React context much before the user moves to a react-native page. For more details, click here.