Mobile app development in San Francisco
Many San Francisco products start on the web and add a mobile app once users ask to take it with them: voice notes that become tasks, photos that become answers, a quick way to act on something the web product flagged. The mobile version needs to feel native, work with poor signal, and pass App Store review with AI-generated content inside it.
We build those apps in React Native, sharing types and API clients with your web codebase so the two do not drift. Voice and image capture upload in the background and resume after interruptions, model responses stream in as they do on the web, and generated content is labelled clearly. We build and run our own mobile product, Amour, so we know what store review and real devices do to a release plan.
San Francisco's software market is, for now, largely an AI market. The city is home to the best-known model companies and to a much larger layer of venture-backed startups building products on top of their models, alongside the SaaS, fintech and developer-tool companies that were here before. Most buyers are young companies with funding, a deadline set by their next raise, and more product ideas than engineers.
What they need is rarely the model. It is everything around it: queues for requests that take most of a minute, streaming that survives a dropped connection, fallbacks when a provider is rate-limiting, a record of what each request cost, and evaluation sets that tell you whether last night's prompt change made things better or worse. Then, often within months, the first enterprise customer arrives, and its IT team asks for single sign-on, automatic provisioning, roles their own admin can manage and an activity log they can export. A backend built for a demo meeting that list is where many pilots stall. We build the product and the infrastructure that make a model useful to paying customers, and the enterprise layer that turns a pilot into a contract.
Built In puts the average base salary for a software engineer in San Francisco at around $181,000, and the model companies compete for the same people with equity most startups cannot match. For a seed or Series A company, every senior hire becomes a search measured in months, and the roadmap waits while it runs. The work that piles up in the meantime is usually well defined: a provider integration, an admin console, a move to usage-based billing, a mobile companion app. That is the work we pick up in days and deliver in pieces you can judge on their own.
We work from Bengaluru with four hours of live overlap every working day, placed across your morning in San Francisco. Stand-ups, design calls and code review happen in that window, with the engineer who writes the code. Everything decided outside it goes into your repository, your tracker and the architecture notes we write as we go, so you start each day knowing what moved.
We fit best when the work is defined and the roadmap will not wait for a hire: the product and infrastructure around a model, the enterprise features a first large customer asks for, or the months before your next engineer starts. Most teams begin with a fixed-price two-week piece. Agencies can bring us in white-label, under their own name.
Four ways this arrives.
And crashes on the ones your users own. We add crash reporting with readable stack traces, find the handful of devices and OS versions causing most of the crashes, and fix those before anyone touches a feature.
Signing keys on a laptop, a manual build, store notes written at midnight. We move builds and signing into CI, add over-the-air updates for JavaScript-only fixes, and write down exactly how a release goes out.
A Bluetooth device, a vendor SDK, a camera pipeline, a background task the OS keeps killing. We write the native module in Swift and Kotlin, expose a small typed interface to React Native, and keep it isolated so upgrades stay possible.
Forms that vanish, actions that send twice. We decide what must work offline, keep it on the device, queue writes with idempotency keys the backend understands, and show the user plainly what is still waiting to sync.
Our own React Native app on Android, with retraction built into the client because moderation can pull a message after it has been sent.
Read the write-up →Asked by San Francisco teams.
How do you work with teams in San Francisco?+
We are in Bengaluru and overlap with you for four hours every working day, placed across your San Francisco morning. Stand-ups, design calls and code review happen live in that window, with the engineer who writes the code. We work inside your tools: Slack for conversation, GitHub for code and review, Linear for the plan. Anything decided outside the window is written down there, so nothing depends on memory.
Do you build for AI startups?+
Yes. Most of that work sits around the model rather than inside it: retrieval over your own data, evaluation sets that run on every prompt change, streaming interfaces, cost tracking per customer, fallbacks between providers, and logging that explains an answer after the fact. Then comes the enterprise layer your first large customer asks for: single sign-on, provisioning, admin roles and activity logs, built so the pilot can become a contract.
How does your rate compare to hiring in San Francisco?+
Built In puts the average base salary for a software engineer in San Francisco at about $181,000, before equity and benefits. Our published rate is $35 an hour, with a $5,000 minimum. There is no recruiting search and no employment overhead, and we can start within days. Most teams begin with a fixed-price two-week piece at $2,800, so you judge us on working code before committing to more.
Can you make our prototype ready for real customers?+
Yes, and it is a common place to start here. A prototype built fast for a demo usually needs the same things: model calls moved into queued, retried jobs, costs recorded per request, tests around the parts that change most, and deploys from CI. We read the code, send a written plan within a week, then take the most urgent piece as a fixed-price two-week job. The repository is yours throughout.
React Native or fully native?+
React Native for most products: one codebase, one team, both stores. Fully native makes sense when the app is mostly the hard native part, such as heavy camera or audio processing, complex background work, or a platform feature React Native does not support yet. We will tell you which side of that line you are on, and write the native parts by hand either way.
Expo or bare React Native?+
Expo, in almost every case now. Development builds and config plugins removed most of the old reasons to eject, and EAS handles builds and signing. We go bare only when a native dependency genuinely cannot live inside a config plugin, and we will explain why before doing it, because it makes every future upgrade more work.
Can you take over an app someone else built?+
Yes. We start by getting it to build on a clean machine, which is often the hardest step, then bring React Native and its dependencies up to a supported version before adding features. We tell you what state the app is in, including where the store listings, signing keys and accounts actually live, before quoting anything larger.
Who handles App Store and Play Store submission?+
We do, from your developer accounts, not ours. We prepare the builds, the privacy disclosures and the notes for the reviewer, and deal with rejections when they come. The accounts, signing keys and listings stay in your name, so you can change developers later without asking anyone's permission.
Does our backend need to change for a mobile app?+
Often, a little. A mobile client stays on old versions for months, retries on bad networks, and cannot be fixed by a server deploy. That means versioned endpoints, idempotent writes, and a way to tell an old client it must update. We check the backend for those before the first screen is built, because retrofitting them after launch is slower.