Server-Driven Mobile Apps With React Native

How do you create a scalable application with lots of different layouts, screens, giving enough flexibility to each team to customise without adding orders of magnitude in complexity to your app? Companies like Airbnb, Meta, and Lyft approach this with server-driven UI. We’ll explore how this can work for mobile apps, challenges that it introduces, and how it’s the way forward in the age of React Server Components. 

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Video Summary and Transcription
The video explores the concept of server driven UI in React Native, highlighting its role in creating scalable and complex UIs. Server driven UI, also known as mobile server side rendering, allows developers to define layouts using a JSON blob from the server, which the React code then dynamically renders. This approach not only reduces code duplication but also simplifies layout management, as seen in the case of Facebook Messenger, where Project Lightspeed helped cut down the codebase significantly. Companies like Shopify, Airbnb, and Lyft leverage server driven UI to achieve platform consistency and dynamic layout control. The talk also touches on the benefits of server driven UI in React Native applications, emphasizing improved performance and flexibility. React Native server driven UI is particularly beneficial for adapting to evolving user requirements without major client-side changes. Server driven UI React enables developers to manage complex UI designs efficiently, making it a popular choice for modern mobile app development.

FAQ

Some challenges associated with server-driven UI include handling caching and offline support, managing the complexity of dynamic layouts, and ensuring seamless integration between server-side and client-side components.

Server-driven UI helps in creating scalable and complex UIs in React Native applications by reducing code duplication and simplifying layout definitions. It allows for dynamic UI updates without requiring significant changes to the client-side code.

Airbnb adopted server-driven UI to achieve platform consistency across web, iOS, and Android. It helped them unify components across different parts of their platform and add new features without significant rework.

Project Lightspeed was an initiative by Facebook to reduce the complexity and size of the Messenger app. By adopting server-driven UI, they were able to cut down from 1.7 million lines of code to 360,000 and reduce the bundle size from 130 megabytes to 30 megabytes.

The advantages of using server-driven UI include reduced code duplication, simplified layout management, dynamic UI updates, and improved performance. It also allows for more flexible and scalable UI designs.

Server-driven UI helped Facebook Messenger reduce code duplication and simplify layout management. This led to a significant reduction in codebase size and bundle size, improving app performance and maintainability.

You can learn more about server-driven UI in React Native by watching talks and presentations from experts. A highly recommended talk is by Evan Bacon from the Expo team, discussing React Server Components within the Expo Router.

In an e-commerce platform like React Cloth, server-driven UI defines the layout using a JSON blob from an API or CMS. This JSON includes various sections like offers, recommended products, and testimonials, which are then dynamically rendered by the client-side code.

Companies like Shopify, Airbnb, and Lyft are using server-driven UI. Shopify uses it for their shop app, Airbnb for platform consistency across web and mobile, and Lyft for dynamically controlling layouts for different user requirements.

Server-driven UI is a design pattern where the server controls the UI layout by sending a JSON blob that defines the layout of the page. This allows for more scalable and complex UIs without significant code duplication.

1. Introduction to Server-driven UI#

Short description:

Today, we are going to be taking a look at server-driven UI and how you can use it within your React Native applications to create more scalable and complex UIs and layouts without incurring a lot of cost and tech debt. The best way to talk about server-driven UI is to go through a very concrete story from the industry. Let's go back in our timelines, back from 2024 all the way to 2019. For the folks at Facebook before they were called meta, they were just releasing out a lot of new features into the messenger app. This app was expanding very quickly, resulting in slow app start-up times and multiple versions of the same UI components.

Hey, everyone. Thank you for joining the session. Today, we are going to be taking a look at server-driven UI, how you can use it within your React Native applications to create more scalable and complex UIs and layouts without incurring a lot of cost and a lot of tech debt.

My name is Mo. I head the mobile team at Theodo. Theodo has been doing React Native since 2015, I believe. We were very early adopters as soon as React Native came out a few months after we started doing React Native. We've been hosting things like the React Native London meetup since 2017. We're very passionate about React Native. We've been in the space for a while, and we've seen a whole host of projects in the React Native space from small to large. Hopefully we can share some of that experience with you all.

The best way to talk about server-driven UI is to go through a very concrete story from the industry. Let's go back in our timelines, back from 2024 all the way to 2019. This was a simpler time. It was the age before the pandemic. Life was simple. For the folks at Facebook before they were called meta, they were just releasing out a lot of new features into the messenger app. If you remember, the logo was blue. It didn't have the gradient. They had just introduced a large group chats. They had added in new functionality and features such as polling. They even added things like maps and games into their app. This app was expanding very, very quickly. As a result, they had over 1.7 million lines of code in the iOS app for Messenger. They had a massive bundle size. We're talking 130 megabytes. All of this resulted in slow app start-up times and also slow run time of the app. There were multiple versions of the same UI components. One thing that they gave an example of was that there were 40 different contactless screens, which is really just the exact same component with slight variations. They had duplicated similar layouts across the app with very minor variations.

2. Project Lightspeed#

Short description:

Project Lightspeed was born as a simpler way to define layouts and UI without hard coding and duplication. The server controls the UI, resulting in a massive reduction in lines of code and bundle size. It also improved team efficiency and introduced a new logo.

Project Lightspeed was born. The whole concept behind Project Lightspeed was that they needed a simpler way to define layouts, to define the UI, that didn't require so much hard coding of different variations, so much code duplication. The strategy that they landed on was this concept of server-driven UI, with a fair bit of more complexity added in for things like caching, offline support. Really the gist of it was that the server controls the UI. If we look at the results, if we go out to 2020, what happened was those 1.7 million lines of code, they were reduced down to 360,000 lines of code. That is a massive reduction. The 130 megabytes of bundle size was reduced down to 30 megabytes of bundle size. They had an entirely new logo, right? Everyone is happy. Really, the gist of it was they were able to cut down so much, speed up their team significantly, all through adopting a different architecture and a different pattern to think about it.

3. Server-driven UI#

Short description:

Server-driven UI allows defining layout and UI using a JSON blob from the server. React code can dynamically render the components based on the server config. Industry players like Shopify, Airbnb, and Lyft use server-driven UI for flexibility in customizing layouts and achieving platform consistency. Server-driven UI enables dynamically controlling the layout as user requirements evolve. Universal React server components play a small part in server-driven UI. Evan Bacon's talk at ReactConf introduces the universal React server components vision.

What is server-driven UI? Let's take a simple example and start to think about this and reason about it. If you have an e-commerce platform, React Cloth, and you look at the layout, oftentimes, the layout are dispersed sections of a screen. There might be an offers section, there might be recommended products, featured categories, testimonials, and a footer.

The whole idea is that we can define a JSON blob that comes from an API or CMS, and that is coming from the server, and it defines the layout of the page. You can see we've got a banner object within this array in the example on the right-hand side, which has a bunch of props, things like the telephone number, the address, the email, so on and so forth. But it might also have a little bit more complexity there. You might have a header, and some of the props include these objects like a menu which is an array of different menu items with their links, and so on and so forth. All of this is coming from the back-end or a CMS that you have.

Now, if we just take an example from this JSON, how do we then implement the React code or React native codes to actually render this? So, we would have almost a components.ts file imports all the different components that you have, and these are individual components, and then we would have a map to say what is the string that's coming from the server that represents that specific component? And then what we would do is we would create almost a generic render component function, and this uses the component map to check the config that's coming from the server and select the right component and pass in the right props that are coming in from the server, sort of dynamically. And then in something like our home page, what we would do is we would get the JSON data, let's say we just use a loader from some React query hook that we've created custom, and then we basically render everything in a map calling the render component. And that ultimately ends up resulting in the layout that we want, and all of that is coming from the server-side.

And if you want to just understand how widespread the usage of server-driven UI is, we can look at some of the big industry players that are using it. So, you've got the likes of Shopify, Airbnb, even though we don't like talking about them because of their whole React Native fiasco, and Lyft. So if we just quickly look at some of the mobile apps that are using this, for Shopify, they have a shop app that basically is a marketplace where different store owners can come and create their own apps. And what they found was different stores with different sizes of items and different amounts of users will need different layouts showing different amounts of products and showing maybe certain bestseller sections for ones that have quite a lot of products. So it was important to be able to customize that so that you started using server-driven UI to give them that level of flexibility.

In Airbnb's case, their entire system of layouting is based off of server-driven UI, and they adopted it because they want a platform consistency across web, mobile, on iOS and Android. Obviously, if they use React Native, maybe they wouldn't need that as much, but the whole idea here was that they could control that with the server and not only sync that across their mobile and web apps, but also have unified components across the host experience to the user experience, to even different parts of the new functionality that they've released, such as the whole experience and stuff that they have where you can go on, let's say, a ship or something for an evening or go to a nice restaurant. So it was more to give them flexibility as they're building up new features to not have to rebuild everything and fall into the same problem that the Messenger team faced.

And lastly, in Lyft's case, it actually was due to the fact that they have this functionality for renting bikes, and this is very widespread in Europe, especially in the Netherlands. But they had this functionality where you rent out bikes, but they wanted to start adding scooters and there was slightly different flows for the bikes versus the scooters. And then they later introduced e-bikes as well. And server-driven UI allowed them to kind of dynamically control that layout as the user requirements were evolving and not need to really do a lot of rework in that process.

You may have seen recently Evan Bacon from the Expo team did a talk about RSCs within the React Native space. And earlier, myself and Evan had a sort of a Twitter exchange where I was talking about server-driven UI and how, you know, doing React on the server does not necessarily always equal RSCs. And, you know, Evan pointed out that RSCs are actually a small part of the server-driven UI universal story. And I couldn't agree more. They fit into a very small part of it. And so, I would highly recommend you watch the talk that Evan did at ReactConf where he's introducing the sort of universal React server components vision within Expo Router. So, that's just the QR code there for you to scan if you want to keep track of that and watch that later. And more generically, I talk about server-driven UI within the React world where I talk about also some of the challenges that come with it and go into a little bit more detail with some of the case studies. So, you can also scan that if you want to keep track of that talk so you can revisit that and go into a little bit more depth about what some of the challenges are and how you combat some of those challenges as you expand your server-driven UI usage within your app.

And thank you very much for joining the talk.

Mo Khazali
Mo Khazali
8 min
18 Jun, 2024

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