Alma
Alma Pay
Designed and built the first version of Alma’s native BNPL app: deferred and split payments, a virtual card and the partner shop directory.
iOSSwift
Native financial product engineering
Senior Fintech iOS Developer
Native iOS engineering for payment, banking and BNPL products where security, authentication, integrations and delivery all have to work together.
Discuss the product Explore the expertise- 2008
- Building digital products since
- 40+
- Apps shipped
- 400M+
- Cumulative downloads
Clément Sauvage · Bits’n Coffee
Native iOS expertise where money moves.
Clément Sauvage is a senior iOS developer and product engineer who designs, builds and ships native financial applications. Since 2008, he has worked on Apple products where the mobile client is part of the financial system: payments, deferred and split payments, strong authentication, partner integrations and App Store delivery.
His fintech work includes designing and building the first version of Alma’s BNPL app, and leading the creation of Crédit Agricole Nord de France’s mobile banking experience in an agency context with a team of three iOS developers. Clément is a Stripe Partner and has contributed to Stripe’s developer community since its early days. Based in France, he works directly with fintech and banking teams in English and French across Europe, the United Kingdom, the United States and Switzerland.
When to bring me in
Ownership for the sensitive parts.
The role is useful when a financial product needs one senior owner connecting the native experience, platform security and the systems behind every transaction.
What does the financial product need?
You need to launch a financial product on iOS
Turn a product definition, banking system or chosen PSP into a native app with a credible architecture, clear authentication and payment states, and a release path prepared for App Review.
Your mobile team needs senior fintech capability
Join an existing team, own the sensitive areas and make the architecture, security and delivery decisions explicit without creating dependency on an external specialist.
The app has become risky to change or release
Assess the codebase and its client-server contracts, identify what is worth keeping and sequence stabilization work while the product continues to move.
Fintech iOS expertise
Security, product and delivery in one system.
The engagement covers the mobile product from architecture to release, with security and regulatory requirements treated as engineering inputs rather than late-stage patches.
Secure native architecture
Design session lifecycles, data minimization, Keychain access, device-generated keys protected by the Secure Enclave, biometric gates and calibrated device-integrity signals from the product’s actual threat model.
Authentication and KYC flows
Build recoverable onboarding, identity-verification hand-offs, strong customer authentication, device binding and the production edge cases created by lost devices, expired sessions and interrupted journeys.
Payments and banking integrations
Integrate Apple Pay, Stripe, Adyen, Mollie and in-house banking APIs across the iOS client and its backend contracts, including 3-D Secure, retries, idempotency and reconciliation.
Native product and App Store delivery
Build in Swift with SwiftUI or UIKit according to the product and codebase, then prepare signing, TestFlight, privacy disclosures, review access and the requirements attached to regulated services.
Technical leadership and handover
Lead product and architecture decisions, guide internal developers or an agency team, coordinate backend and specialist contributors, and leave code and conventions the organization can own.
Verified fintech experience
Financial products shipped in production.
Two native engagements spanning BNPL, mobile banking, platform integration and team leadership.
Crédit Agricole Nord de France
Crédit Agricole Nord de France
Led the creation and delivery of the mobile banking experience in an agency context, managing three iOS developers across the iPhone app and Apple Watch companion.
iOSSwift
Engineering principles
Model the risk. Make the states explicit. Ship deliberately.
The security and process should match the product: a BNPL checkout, a banking app and a financial tracker do not share the same threat model or regulatory perimeter.
- 01Model
Threat model before architecture
Identify what is protected, who could attack it and the consequences of failure before choosing controls, storage, authentication and client-server boundaries.
- 02State
Treat money movement as a state machine
Define transitions, retries, timeouts and reconciliation across the app, backend and PSP so the interface reflects a durable transaction model instead of owning it.
- 03Align
Translate compliance into product requirements
Work with legal, risk and compliance teams to turn their decisions into testable flows and technical constraints without presenting engineering as regulatory advice.
- 04Transfer
Leave the team in control
Document the decisions, establish maintainable conventions and transfer enough context for the internal team to operate and evolve the product after the engagement.
Frequently asked questions
Clear before the first transaction.
The regulatory perimeter, system responsibilities and delivery model should be explicit before architecture begins.
What makes fintech iOS development different?
The mobile client sits inside a wider risk and regulatory system. Authentication, secure storage, payment state, partner APIs and App Store requirements must work together without making the product slow or difficult to recover.
Which payment providers do you work with?
Clément is a Stripe Partner and has also worked with Adyen, Mollie and in-house payment or banking APIs. Provider selection remains a business decision; the engagement covers the mobile integration and the contracts it needs from the backend.
Can you implement strong authentication and KYC?
Yes. The work can cover SCA, biometric and device-bound authentication, identity-provider hand-offs, document or liveness journeys and recovery paths. Compliance, risk and legal teams define the applicable requirements; Clément translates them into the product.
Should a fintech app be native or cross-platform?
For a new financial product where Apple Pay, device identity, platform security and native interaction are central, native iOS is Clément’s preferred starting point. An existing cross-platform app should be assessed on evidence rather than rewritten on principle.
Do you advise on regulatory compliance?
No. Clément understands the technical context around SCA, KYC, AML and data protection, but compliance decisions remain with the company’s legal, risk and compliance teams. His responsibility is to implement those requirements faithfully in the product.
Tell me what moves through the product.
I’ll tell you how I would build it.
Share the financial product, the banking or payment systems involved, the current team and what needs to ship. I’ll personally review the context and explain how I would approach the iOS build.
Discuss the product