--- title: "Architecture & Performance" description: "We help products get past technical limits that slow delivery and hurt quality. Senior engineers solve the underlying issues so teams can ship faster with more confidence." url: https://www.callstack.com/capabilities/architecture-performance updated: 2026-11-06T10:07:33.274Z --- # Architecture & Performance We help products get past technical limits that slow delivery and hurt quality. Senior engineers solve the underlying issues so teams can ship faster with more confidence. _[Expert Engineering](https://www.callstack.com/ai-native-engineering) › Architecture & Performance_ **Solve your hardest engineering challenges.** We help products get past technical limits that slow delivery and hurt quality. Senior engineers solve the underlying issues so teams can ship faster with more confidence. [Book consultation](https://www.callstack.com/contact) [Explore services](#services) Trusted by 100+ Enterprise clients Expensify · Ticketmaster · DirecTV · MLS · PWC · Evernote · AutoZone · MoMo · Dream11 · Rainbow · Futurewei · RIMAC · Hello Fresh · Haaretz · ForaTravel · CelcomDigi · Teamworks · Boats · Questrade · Dialogue Why solve it with Callstack ## Fix the limits blocking delivery. Senior engineers trace the root causes behind slow, flaky, or hard-to-ship code. We handle demanding native and architecture work without pulling your roadmap off course. - **Improve speed and stability.** Fix the issues that hurt user experience and release confidence. - **Remove engineering bottlenecks.** Solve architecture and codebase problems that slow delivery down. - **Get the hard work done.** Senior engineers handle demanding native and low-level work without derailing the roadmap. - **Strengthen the foundation.** Leave the product easier to maintain, extend, and ship from. Services ## Fix the engineering limits blocking delivery. ### Performance - [React Native Performance Optimization](https://www.callstack.com/services/react-native-performance-optimization): Profile and tune React Native apps to find the bottlenecks behind slow starts, dropped frames, and memory leaks. - [AI Vibe Coding Cleanup](https://www.callstack.com/services/ai-vibe-coding-cleanup): Review and refactor code written by AI tools before it ships, where fast output often hides missing edge cases, weak patterns, and architectural shortcuts. ### Native & Low-Level - [React Native Modules Development](https://www.callstack.com/services/react-native-modules-development): Build custom native modules in Swift, Kotlin, and Objective-C when the JavaScript layer cannot reach the platform capability the product needs. - [React Native Brownfield Integration](https://www.callstack.com/services/react-native-brownfield): Embed React Native inside an existing native iOS or Android app, adding new screens and features without rewriting the surrounding codebase. - [C++ Library Integration](https://www.callstack.com/services/c-library-integration-for-react-native): Bring existing C++ libraries into React Native through JSI, giving the app access to shared cross-platform logic and performance-critical code. - [Shared Native Core](https://www.callstack.com/services/shared-native-core-for-cross-platform-apps): Build one C++ or Rust core for mobile, web, desktop, and TV so teams avoid per-platform rewrites and logic drift. - [Custom High-Performance Renderers](https://www.callstack.com/services/custom-high-performance-renderers): Build specialized rendering engines for graphics, media, and immersive experiences where off-the-shelf components cannot meet the performance the product needs. Architecture & Performance ## Get an architecture review. Point us at the code that's slow, flaky, or hard to ship. Our senior engineers come back with root causes and a prioritized fix plan. [Book a call](https://www.callstack.com/contact) How we work together ## Turn technical limits into shipped fixes. ### Extend your team Our senior engineers join your team to ship features, guide technical decisions, and strengthen delivery. - Your roadmap and workflow - Expertise shared as we work - Flexible timezone coverage ### Deliver a project We take agreed work from technical planning to release, with clear responsibilities and progress you can see. - 3 Callstack engineers ship like 6 - Impact visible before sprint two - End-to-end delivery ### Solve specific challenge We address a performance, migration, or infrastructure challenge, or run training around your team’s needs. - Focused reviews or implementation - Knowledge your team keeps - Outcomes guaranteed with contract - React Foundation Founding Member · 300+ commits to React Native · Contributing since 2016 - Industry runs on our tooling · 50M+ OSS downloads / month - [5x Faster message sending time](https://www.callstack.com/case-studies/enhancing-applications-performance-for-expensify) - [-28% CPU usage in critical trading flows](https://www.callstack.com/case-studies/migrating-questrade-edge-mobile-to-a-faster-more-scalable-architecture) - “Our app has hundreds of features and before we switched to Re.Pack we were struggling to scale the performance. Re.Pack is built on Webpack, so it allowed us to leverage existing tooling and approaches to scale more linearly. If the default tooling isn't working for your use case, I'd recommend giving Re.Pack a try!” — Mike Duminy, Principal Engineer / Klarna - 100+ Enterprise projects delivered Case studies ## What shipping at AI speed looks like ### [Migrating Questrade Edge Mobile to a Faster, More Scalable Architecture](https://www.callstack.com/case-studies/migrating-questrade-edge-mobile-to-a-faster-more-scalable-architecture) Expert Engineering · Finance **33%** fewer re-renders across most features ### [Building scalable observability for a high-growth React Native app](https://www.callstack.com/case-studies/building-scalable-observability-for-a-high-growth-react-native-app) Agentic Delivery · Finance **3→1** analytics systems unified into a single interface ### [Building an Agentic SDLC for a Web Launch in Under One Month](https://www.callstack.com/case-studies/building-an-agentic-sdlc-for-a-web-launch-in-under-one-month) Agentic Delivery · Software Development **3x** estimated delivery acceleration ### [Launching a High-Performance React Native app on Samsung TV](https://www.callstack.com/case-studies/launching-samsung-tv-app-for-global-streaming-platform) Expert Engineering · Media & Streaming **5** platforms under one RN codebase: tvOS, FireTV, Tizen, LG, Vizio ### [Improving Chat Performance and Creating a Custom UI Library](https://www.callstack.com/case-studies/improving-chat-performance-for-dream11) Expert Engineering · Sports & Entertainment **78%** bundle size reduction (from 50 MB to 11 MB) ### [Creating React Native SDK wrapper](https://www.callstack.com/case-studies/creating-react-native-sdk-wrapper-for-rive) Expert Engineering · Software Development **100k** weekly downloads on npm ### [Enhancing Expensify app performance](https://www.callstack.com/case-studies/enhancing-applications-performance-for-expensify) Expert Engineering · Finance **5x** faster message sending time ### [Migrating to Next.js for better performance and SEO](https://www.callstack.com/case-studies/migration-to-nextjs-for-autozone) Expert Engineering · Automotive **#1** SEO rank, recovering from 3-9 ### [Training HelloFresh engineers to build production apps with React Native](https://www.callstack.com/case-studies/training-hellofresh-engineers-to-build-production-apps-with-react-native) Expert Engineering · Retail & E-commerce **2.8x** increase in knowledge over 8 weeks (25% → 71% assessment scores) ### [A brownfield architecture that kept feature delivery moving across financial apps used by millions](https://www.callstack.com/case-studies/modernizing-mobile-apps-in-production-with-react-native-and-self-hosted-ota) Expert Engineering · Finance **4x** increase in RN pages across the tracked page set ### [Optimizing Android TV startup by disabling JS bundle compression](https://www.callstack.com/case-studies/optimizing-android-tv-startup-for-global-streaming-platform) Expert Engineering · Media & Streaming **5%** faster startup time on FireTV and FireHD devices 10 years of React Native → Now in your AI stack ## Get an architecture review. Point us at the code that's slow, flaky, or hard to ship. Our senior engineers come back with root causes and a prioritized fix plan. [Book a call](https://www.callstack.com/contact) Open Source ## Build with our open-source tools. We open-source the tools behind our delivery model. Use them, fork them, or let us run them for you. [Check All Tools](https://www.callstack.com/open-source) [Explore AI Infrastructure](https://www.callstack.com/capabilities/self-hosted-ci-cd-infrastructure) - [Reassure](https://github.com/callstack/reassure): Performance testing companion for React and React Native (1.5K stars) - [React Native Harness](https://github.com/callstackincubator/react-native-harness): Harness brings Jest-style tests to real native environments so you can test TurboModules like you would test your React Native app: with JavaScript. (179.7K downloads/mo) - [Rozenite](https://github.com/callstackincubator/rozenite): Plug-and-play panels for React Native DevTools. Install, enable, and start debugging in minutes. (959.8K downloads/mo) - [Re.Pack](https://re-pack.dev/): A webpack-based toolkit to build your React Native application with full support of webpack ecosystem (2.2M downloads/mo) - [React Native Sandbox](https://github.com/callstackincubator/react-native-sandbox): Run multiple, isolated React Native instances within a single application (15.4K downloads/mo) - [React Native Brownfield](https://github.com/callstack/react-native-brownfield): Incrementally move your iOS and Android apps to React Native without breaking (552 stars) - [Agent Skills](https://github.com/callstackincubator/agent-skills): Callstack’s best practices on React Native performance optimization, upgrading, CI workflows, and brownfield migrations (1.7K stars) Insights ## Worth your time, by engineers. [Explore Insights](https://www.callstack.com/insights) - [Efficient On-Device LLMs in React Native Done Right](https://www.callstack.com/events/efficient-on-device-llms-in-react-native-done-right) (Nov 17 · Talk): Artur Morys-Magiera will cover efficient on-device LLMs in React Native, including runtimes, model selection, quantization, and platform constraints. - [On-Device AI After WWDC: What Changed for React Native](https://www.callstack.com/events/on-device-ai-after-wwdc-what-changed-for-react-native) (Nov 17 · Talk): Mike Grabowski will explain what changed for system-provided on-device AI after WWDC and what React Native developers can build with it. - [Building a Modern Navigation Library: The Hard Parts](https://www.callstack.com/events/building-a-modern-navigation-library-the-hard-parts-2) (Oct 7 · Talk): At reactCon, Satyajit Sahoo explores the design choices behind React Navigation 8 and the challenges of creating a navigation library that works across platforms. - [JSX to Live Activity: The Story of Voltra](https://www.callstack.com/events/jsx-to-live-activity-the-story-of-voltra-react-native-connection-2026) (Sep 24 · Talk): Szymon Chmal will show how Voltra brings iOS Live Activities and widgets to React Native without requiring developers to write native UI code. - [Building a Modern Navigation Library: The Hard Parts](https://www.callstack.com/events/building-a-modern-navigation-library-the-hard-parts) (Sep 24 · Talk): Satyajit Sahoo will share the decisions and trade-offs behind React Navigation 8 and building a modern cross-platform navigation library. - [Running AI in the Browser With Transformers.js](https://www.callstack.com/podcasts/running-ai-in-the-browser-with-transformers-js) (Sep 7 · Podcast): Nico Martin explains how Transformers.js uses WebGPU and ONNX to run AI in the browser, plus the limits of local models and on-device agents. - [VisionCamera V5 With Marc Rousavy](https://www.callstack.com/podcasts/visioncamera-v5-with-marc-rousavy) (Aug 4 · Podcast): Marc Rousavy joins Mike Grabowski to unpack VisionCamera v5, Nitro Modules, the constraints API, migration work, and what changed for React Native camera apps. - [An AI Agent for Measured React Native Performance Fixes](https://www.callstack.com/blog/an-ai-agent-for-measured-react-native-performance-fixes) (Jul 20 · Article): React Native performance work can produce misleading results when teams rely on a single profiler run. This article introduces Metrognome, an open-source AI plugin that turns proposed fixes into repeated, gated experiments on a live app. It explains how the tool combines device control, render analysis, runtime signals, and performance guidance, shares examples from Uphold, and shows how its Performance Map and CI workflows prioritize issues and create evidence-backed PRs.