Mobile app development that passes technical due diligence .

Your investors will audit your app before they fund you. Most startups fail this audit. We build apps that pass—so you close your round.

$27M+ Raised
200K+ Users Scaled
99% Crash-Free

Why mobile apps kill funding rounds.

You've raised Seed. Your app works—barely. It crashes during demos. Reviews sit at 2.8★. Load times hit 8 seconds.

Now you're raising Series A. VCs will audit your code. They'll find:

  • Tech debt that costs $200K+ to fix
  • Security holes that risk user data
  • Performance issues that prevent scale

Every week you wait burns $50-100K in runway.

Get Your Free Technical Audit

We'll tell you exactly what's broken and how to fix it.

How we build apps that pass due diligence.

Technical Audit & Architecture

We map your current app, find what breaks at scale, and design the fix. You get a technical roadmap investors trust.

Timeline: 2 weeks.

Rebuild Core Infrastructure

We rebuild your app foundation to handle 200K concurrent users. React Native + TypeScript for stability. Full error tracking and monitoring.

Timeline: 8-12 weeks.

Security & Compliance

We implement authentication, encrypt user data, and close security vulnerabilities. You pass SOC 2 and GDPR audits.

Timeline: 4 weeks.

Performance Optimization

We cut load times from 8 seconds to under 2. We reduce crashes to under 1%. We fix the bugs that kill your ratings.

Timeline: 4-6 weeks.

Investor-Ready Documentation

We document your architecture, write technical specs, and create the materials VCs review during due diligence.

Timeline: 2 weeks.

The Vermillion difference.

Traditional Agency Vermillion
Junior devs learning on your dime Senior engineers (10+ years)
Monthly retainers, no guarantees Performance pricing—you win, we win
Disappear after launch Hand you trained team, walk away
Build what you ask for Tell you what you actually need
Bill hourly forever Fixed scope, clear timeline
Schedule a Strategy Call

Let's discuss your mobile app development needs.

React Native app development for Series A startups.

We specialize in React Native because it lets you build iOS and Android apps from one codebase. You ship faster. You maintain less code. You scale more efficiently.

Why React Native for funded startups:

  • Single codebase for iOS and Android cuts development time 40%
  • TypeScript integration catches bugs before production
  • Hot reloading speeds up development and testing
  • Native performance without native complexity
  • Massive ecosystem means faster feature development

Most agencies treat React Native like a website. We build native-quality apps that perform like they were written in Swift or Kotlin.

What we build:

  • • Consumer social apps that handle millions of users
  • • Marketplace apps with real-time transactions
  • • Health and fitness apps that sync with wearables
  • • Fintech apps that pass security audits
  • • B2B apps that integrate with enterprise systems

Technical stack:

  • • React Native 0.73+ with TypeScript
  • • Zustand for state management
  • • React Query for server state and caching
  • • Expo for rapid iteration
  • • Jest and React Native Testing Library (80%+ coverage)
  • • Sentry or Bugsnag for error tracking

Ready to build a React Native app that scales?

Let's map out your technical roadmap and timeline.

Start Your Project

iOS and Android native app development.

Sometimes React Native isn't the answer. When you need maximum performance or deep platform integration, we build native.

When to build native:

  • Your app processes video or audio in real-time
  • You need advanced AR or camera features
  • You're building for Apple Watch or Android Wear
  • You require complex background processing
  • Performance is more important than speed to market

iOS development:

We write Swift (not Objective-C). We follow Apple's Human Interface Guidelines. We optimize for every iPhone and iPad. Your app feels like it belongs on iOS.

Android development:

We write Kotlin (not Java). We follow Material Design principles. We test on real devices—not just emulators. Your app works on Samsung, Google, OnePlus, and everything else.

Native stack:

  • • Swift 5.9+ and SwiftUI for iOS
  • • Kotlin 1.9+ and Jetpack Compose for Android
  • • Core Data or Realm for local storage
  • • URLSession or Retrofit for networking
  • • XCTest and Espresso for automated testing
  • • Firebase for analytics and crash reporting

Cross-platform mobile app development strategy.

The question isn't "React Native vs native." It's "what gets you to Series A fastest."

We recommend React Native when:

  • • You're pre-Series A with limited budget
  • • Time to market matters more than perfect performance
  • • Your app is content-driven or business logic heavy
  • • You need one team to maintain both platforms
  • • You're testing product-market fit

We recommend native when:

  • • You've raised Series A and need to differentiate
  • • Your app requires maximum performance
  • • You're deeply integrating with platform features
  • • You have separate iOS and Android user bases
  • • You're optimizing for retention over acquisition

We recommend hybrid (React Native + native modules) when:

  • • You need speed to market but also custom features
  • • 80% of your app is standard, 20% requires native code
  • • You want to share business logic but customize UI
  • • You need specific iOS features not available in React Native

Most of our clients start with React Native. When they raise Series A or B, we help them decide if native makes sense. We've done both paths dozens of times.

Get Expert Platform Advice

We'll help you choose the right approach for your startup.

Custom backend development for mobile apps.

Your app is only as good as your backend. We build APIs that scale to millions of users using Python, NestJS, or Go.

Python + FastAPI:

  • • Best for data-heavy apps and ML integration
  • • Fast async performance
  • • Type safety with Pydantic
  • • Excellent for startups with data science needs

NestJS + TypeScript:

  • • Best for TypeScript teams (share types with frontend)
  • • Structured architecture that scales
  • • Built-in validation and documentation
  • • Excellent developer experience

Go:

  • • Best for high-performance microservices
  • • Handles millions of concurrent requests
  • • Low memory footprint
  • • Excellent for real-time features

How we choose: If your team writes TypeScript, we use NestJS. If you need ML or data processing, we use Python. If you need maximum performance, we use Go. Most startups start with NestJS or Python.

Database options:

  • PostgreSQL: Relational data with complex queries
  • MongoDB: Flexible document storage
  • Redis: Caching and real-time features
  • DynamoDB: Serverless NoSQL at scale

What we build:

  • • RESTful APIs with OpenAPI documentation
  • • GraphQL endpoints for complex data needs
  • • Real-time features with WebSockets
  • • Authentication and authorization systems
  • • Push notification infrastructure
  • • Background job processing
  • • Admin dashboards for content management

Infrastructure:

  • • AWS or Google Cloud Platform
  • • Docker containers for consistency
  • • CI/CD pipelines for rapid deployment
  • • Auto-scaling for traffic spikes
  • • Monitoring and alerting (DataDog, Sentry)
  • • Database backups and disaster recovery

Expo and over-the-air updates.

We build with Expo because it gives you superpowers other agencies can't match.

Why Expo:

  • Faster development: Built-in components and APIs
  • Instant updates: Fix bugs without app store review
  • Easy testing: Share builds with TestFlight and Play Store alternatives
  • Native module access: Drop to bare workflow when needed
  • Push notifications: Built-in infrastructure
  • OTA updates: Deploy fixes in minutes

Expo Updates for instant deployments:

You find a critical bug. With traditional apps, you submit to app stores and wait 24-48 hours. With Expo Updates, you push a fix and users get it in minutes.

What you can update over-the-air:
  • • Bug fixes in JavaScript/TypeScript code
  • • UI changes and improvements
  • • Business logic updates
  • • API endpoint changes
  • • Feature toggles
  • • A/B test variations
What you can't update:
  • • Native code changes
  • • New native dependencies
  • • iOS or Android configuration

Real-world impact:

PicklePlay found a crash affecting 15% of users on Friday night. We pushed a fix via Expo Updates in 20 minutes. By Saturday morning, 98% of users had the update. No app store submission needed.

When we don't use Expo: If you need complex native modules or custom native code, we use bare React Native workflow. But 80% of apps don't need this.

Build with Expo Updates

Ship faster and deploy fixes instantly with our Expo expertise.

PicklePlay: 10K users to 200K users in 12 weeks.

The Challenge:

PicklePlay had 10K users but their app was broken. Crashes hit 30% of sessions. Reviews averaged 2.8★. Poor architecture made every new feature take weeks. Their Series A was stalled—investors saw the crash reports and walked away.

What We Did:

We rebuilt their React Native app from the ground up. Implemented Zustand for clean state management. Built a new Python backend with proper API design. Added Sentry for error tracking and fixed root causes systematically. Optimized database queries that were killing performance. Reduced crashes from 30% to under 1%.

The Result:

Crash rate:

30% → 0.8%

App rating:

2.8★ → 4.5★

Users:

10K → 200K

Exit:

Acquired by UTR

"Vermillion rebuilt our app in 12 weeks. We went from losing users daily to 200K active users. UTR acquired us shortly after."

— Blake Renaud, Founder, PicklePlay

Ready to scale like PicklePlay?

Get Your Success Roadmap

Timeline & Investment.

Week 1-2: Technical Audit

We audit your app, map problems, and create your rebuild roadmap. You get a technical document that shows investors you have a plan.

Week 3-14: Core Rebuild

We rebuild your infrastructure to handle scale. You get weekly demos showing progress. Your app becomes stable enough to grow.

Week 15-18: Polish & Documentation

We optimize performance, write documentation, and train your team. You're ready for technical due diligence.

Week 19-20: Handoff

We hand you a trained team and walk away. You own the code. You know how to maintain it.

Investment: $400K-$600K depending on scope.

Most clients use unspent R&D credits.

Discuss Your Timeline

Mobile app development cost breakdown.

MVP development: $80K-$150K

  • • 8-12 weeks
  • • One core feature
  • • iOS and Android via React Native + Expo
  • • Custom backend (Python, NestJS, or Go)
  • • App store launch

Full product rebuild: $400K-$600K

  • • 16-20 weeks
  • • Complete infrastructure overhaul
  • • Performance optimization
  • • Security and compliance
  • • Team training and handoff

Ongoing maintenance: $8K-$25K/month

  • • Bug fixes and updates (via Expo Updates)
  • • OS compatibility
  • • Security patches
  • • Performance monitoring
  • • Feature additions (higher tiers)

Why we cost more than offshore agencies

We're senior engineers with 10+ years experience. We've built apps that raised $200M+. Cheap agencies create tech debt that costs 3x to fix later.

Payment options

  • • Upfront payment with milestone deliverables
  • • Split payment (50% start, 50% completion)
  • • Use unspent R&D tax credits
  • • Equity + cash for exceptional founders (rare)
Get Pricing for Your Project

Transparent pricing. No hidden fees.

Mobile app development process.

Week 1: Discovery & Planning

Interviews, code review, user flows, risk mapping. You get a project brief and technical roadmap.

Week 2: Design & Architecture

Wireframes, key screens, API definitions, schema, integrations. You approve before build.

Week 3-16: Development (Sprints)

2-week sprints with Friday demos. You test, give feedback, we adjust.

Week 17-18: Testing & QA

Automated + manual + performance testing on 20+ devices. Prep for app store submission.

Week 19-20: Launch & Handoff

Submit to stores, train your team, hand over docs, credentials, infra. You own everything.

See how we'd approach your project

Get a customized development plan and timeline.

Request Your Plan

How we're different from other agencies.

Most agencies:

  • • Assign junior developers to keep costs low
  • • Bill monthly retainers with no accountability
  • • Build what you ask for without questioning it
  • • Disappear after launch
  • • Focus on features over outcomes
  • • Use Redux because that's what they know

Vermillion:

  • • Only senior engineers (10+ years experience)
  • • Performance-based pricing—you win, we win
  • • Tell you what you actually need, not what you asked for
  • • Train your team and hand off completely
  • • Focus on passing due diligence and closing rounds
  • • Use modern tools (Zustand, Expo Updates) that make you faster

Common mobile app development mistakes that kill funding rounds.

  • Mistake 1: Building too many features — Unfocused strategy and tech debt.
  • Mistake 2: Ignoring performance — Crashes on older devices kill retention.
  • Mistake 3: No automated testing — Users find bugs, ratings suffer.
  • Mistake 4: Weak security — Fail audits, round dies in diligence.
  • Mistake 5: No documentation — Single point of failure risk.
  • Mistake 6: Premature optimization — Build for 10x, not 100x.
  • Mistake 7: Wrong tech stack — Needless boilerplate slows delivery.
  • Mistake 8: Offshore development — Cheap now, expensive later.

Avoid these mistakes. Work with senior engineers.

Talk to Our Team

Mobile app development for specific industries.

Healthcare and telemedicine

  • • HIPAA compliance
  • • EHR integrations
  • • Secure video calls
  • • Wearable integration

Fintech and payments

  • • PCI DSS compliance
  • • Plaid or Stripe integration
  • • KYC and identity verification
  • • Transaction processing

Social and community

  • • Real-time messaging
  • • Moderation and UGC
  • • Push notification systems

Marketplace and e-commerce

  • • Payment processing
  • • Inventory management
  • • Search, filtering, reviews
  • • Order tracking

Fitness and wellness

  • • Wearable sync
  • • Activity tracking
  • • Subscriptions
  • • Health data privacy
Discuss Your Industry Needs

We'll show you relevant case studies and technical approaches.

Is this for you?.

You're Ready If:

  • ✓ You've raised Seed or Series A
  • ✓ You're preparing for your next funding round
  • ✓ Your app has PMF but technical problems
  • ✓ You have $400K+ budget or unspent R&D credits
  • ✓ You need to start in the next 30 days

You're Not Ready If:

  • ✗ You're pre-revenue or pre-product
  • ✗ You have a strong engineering team already
  • ✗ You're optimizing for cheapest option
  • ✗ You can't make decisions in under 2 weeks

We work with 12 clients per year. Seven spots left for 2025.

Claim Your Spot

Limited availability. Book your strategy session now.

Frequently asked questions.

How long does mobile app development take?

MVP: 8-12 weeks. Full product: 16-20 weeks. Timeline depends on complexity and how fast you make decisions.

Do you develop iOS and Android apps?

Yes. We build both using React Native (single codebase) or native development (separate codebases). We recommend React Native + Expo for most startups.

Can you take over an existing app?

Yes. We audit your current app, identify problems, and create a rebuild plan. Most apps need significant refactoring before they can scale.

Do you provide ongoing support after launch?

Yes. We offer maintenance plans starting at $8K/month. Or we train your team and hand off completely.

What's included in the $5,000 strategy session?

Technical audit, due diligence gap analysis, rebuild roadmap, timeline estimate, and investment breakdown. If we work together, the $5,000 applies to your project.

Can you help us pass technical due diligence?

That's our specialty. We've helped clients pass due diligence and close $27M+ in funding.

What happens next.

Book a strategy session. We'll audit your app for free and tell you exactly what needs fixing. You'll get a technical roadmap and timeline. If it's a fit, we start in 30 days.

No pressure. No sales pitch. Just honest advice from engineers who've done this 40+ times.

Book Strategy Session

Session covers:

  • • Technical audit of your current app
  • • Gap analysis for due diligence
  • • Rebuild roadmap and timeline
  • • Investment estimate and payment options

If we work together, the $5,000 applies to your project.