React Native at Scale With Mike Duminy

Duminy describes Klarna as a shopping and payments company whose app lets customers shop, pay, track deliveries, and use rewards. The company handles more than 2 million purchases a day and has over 150 million customers; its app has about 30 million monthly active users. Duminy says teams use instrumentation and A/B tests to understand behavior and measure changes against KPIs.

Klarna’s shared monorepo supports its React Native app, web app, internal apps, and browser extension. Duminy says shared UI, logic, types, and tooling make it easier to support multiple platforms and help feature developers work through common abstractions. Re.Pack provides access to Webpack features such as tree shaking and code splitting; the app’s production JavaScript bundle is about 40 to 50 MB, compared with roughly 110 MB in development mode.

Duminy recalls a performance push that brought Android startup time from nearly 30 seconds to about 2.5 seconds, while iOS startup is now under a second. He says Re.Pack was one part of a broader effort, so the improvement cannot be attributed to it alone. Klarna releases the public app weekly and uses a custom Re.Pack based process to send smaller JavaScript updates when urgent fixes are needed, targeting updates to specific app versions.

Duminy describes around 70 teams working in the client codebase, with the broader React Native group ranging between 350 and 500 people. Teams own vertical slices of customer problems, including the related client and backend work, and can set their own KPIs. In the monorepo, package.json fields assign ownership through roughly 4,000 workspaces, and a merge checker identifies the teams responsible for changed files.

Klarna wants customers to move between products and platforms while keeping a cohesive experience. Duminy says the goal is for a feature team to build a Klarna feature that can run across the app, web, browser extension, and other touchpoints. The team is exploring Module Federation to resolve parts of the app at runtime, support independent deployment, and share dependencies.