Building payments at scale
I build iOS products that make complexity disappear.
Senior Software Engineer (iOS) building products across Wolt, DoorDash, and Deliveroo. I work end to end, from clean architecture and modular SDKs to considered interfaces, purposeful motion, and measurable performance. Payments is where I go deepest: 30+ payment methods, 22 providers, every checkout flow.
- Architecture & modular SDKs
- UI & interaction craft
- Performance
- Design systems
- Accessibility
- Testing & automation
- FinTech & payments
Aamir Suhial Mir
Senior Software Engineer (iOS)
10+ yrs engineering · 7+ yrs iOS · 3+ yrs FinTech
About
Engineering complex systems with clarity.
Architecture, product craft, and payments built end to end.
Senior Software Engineer (iOS)
I build iOS systems that make complex payments feel effortless.
At Wolt | DoorDash, I work across architecture, product craft, and payment reliability while building one unified SDK for three global brands.
My approach combines systems thinking from TU Berlin with a decade of software engineering: clear boundaries, measurable performance, and interfaces that feel considered.
- Architecture
- FinTech
- Product craft
Payments at scale
30+
Payment methods
22
Payment providers
3
Global brands
1
Unified payments SDK
Berlin, Germany · TU Berlin
English · German · Kashmiri
Experience
Where I've shipped
A decade of building iOS products across FinTech, health, e-commerce, and enterprise.
Currently
Senior Software Engineer
Wolt | DoorDash
Berlin, Germany
Payments and FinTech. I own the iOS payments surface, the layer between a customer tapping
“Pay” and money actually moving. More than 30 payment methods and
22 payment service providers, unified behind one cross-brand SDK.
- The full payment lifecycle. Tokenizing a card so raw PAN never touches the app, authorizing against an acquirer, handling the 3DS/SCA challenge when the bank demands it, surviving the redirect out to a third party and back, then reconciling the result. Every step has its own failure mode, and a payment that fails silently is worse than one that fails loudly.
- One SDK, many providers. Every PSP models the same concepts differently. Some want a nonce, some a session, some hand you a web view and wish you luck. I designed the abstraction that normalizes them behind a single protocol-driven interface, so adding a provider is a conformance, not a rewrite of checkout.
- Providers and regional rails. Integrated Adyen, Finaro, Stripe, Braintree, Spreedly, ProcessOut, Worldpay, Juspay, and market-specific benefit schemes including SZÉP cards.
- Wallets, redirects, and meal benefits. Apple Pay and device-attested wallets, bank-redirect methods across European markets, BNPL, gift cards and stored balance, tipping, and employee benefit schemes across products with their own regulatory shape, currency rules, and market availability.
- Beyond card checkout. Built gift cards, balance top-ups, account credits, and corporate invoicing flows. Each has distinct funding, eligibility, and reconciliation rules.
- Server-driven checkout UI. Built the payment sheet as a slot-based rendering engine fed by the backend, so a new method can launch in a market without shipping an app release. Cuts the feature-to-customer latency from an App Store cycle to a config change.
- Cross-brand by design. One codebase serving three consumer apps with different brands, markets, and native payment stacks. That means the boundaries have to be real. Protocol seams and dependency injection over shared mutable state.
- Correctness you can prove. Payments is the worst place to find out you were wrong in production. I built the E2E automation pipeline for payment flows in CI, drove characterization tests ahead of refactors, and treated testability as a product requirement rather than a nice-to-have.
- Modernizing while shipping. Migrated payment modules to Swift 6 strict concurrency, decomposed monolithic view controllers into a presenter/slot architecture across a sequenced series of small reviewable changes, with no big-bang rewrite or feature freeze.
- Regulated, audited, gated. Work under PCI constraints, age and jurisdiction restrictions, and market-specific compliance rules. Behavior changes roll out behind feature flags and experiments so nothing ships as a coin flip.
- Cross-functional delivery. Aligned iOS with Android and backend across three consumer brands, so every platform agrees on what a payment is and how it should behave.
Lead Software Engineer, iOS
Astrivis
Zurich, Switzerland
Led iOS engineering at a Zurich-based startup that transforms smartphones into professional 3D scanners
used in orthotics, prosthetics, custom footwear, and eyewear. Laid the technical foundation for
Astriscan.
- Built the iOS 3D scanning experience with real-time live feedback and quality assessment during capture
- Implemented on-device 3D model generation, giving users an instant preview in under 30 seconds without cloud dependency
- Integrated RGBD camera APIs for body-part scanning with mm-level accuracy
- Defined architecture, technical direction, and development workflow for the mobile product
Technical Lead, Senior Software Engineer
kfzteile24 GmbH
Berlin, Germany
Led the iOS team at Germany's leading online auto parts retailer. Drove architecture decisions, mentored engineers, and shipped a high-performance e-commerce app.
- Led iOS architecture migration and established clean modular patterns
- Managed code review processes and mentored junior & mid-level engineers
- Shipped e-commerce features: product search, checkout, order tracking
iOS Engineer
AMBOSS
Berlin, Germany
Ground-up rewrite of the world's leading medical education platform, used by doctors and students in 180+ countries. Rebuilt it on a scalable architecture with carefully crafted motion and a genuinely considered reading experience across both the knowledge library and the Q-Bank exam prep app.
iOS Developer
Cortado Holding AG
Berlin, Germany
Developed enterprise mobile device management and cloud printing solutions. Shipped the Cortado MDM app and ThinPrint Personal Printing.
iOS Developer
Tignum
Berlin, Germany
Built the iOS app for an executive performance coaching platform focused on sustainable high performance, resilience, and well-being.
Junior iOS Developer (Intern)
Newsenselab GmbH
Berlin, Germany
First professional iOS role. Built foundational skills in Swift development and shipped production features during a focused internship.
Apps
Apps I've shipped
Consumer products across delivery, healthcare, e-commerce, and enterprise.
Wolt
Food delivery & more. 30M+ users across 25 countries.
App Store
DoorDash
Food, grocery & more. America's largest delivery platform.
App Store
Deliveroo
Food & shopping delivery across UK, Europe & beyond.
App Store
Astriscan
Turns a phone into a professional 3D scanner with no extra hardware.
App Store
AMBOSS Knowledge
Medical reference library for doctors & students in 180+ countries.
App Store
AMBOSS Q-Bank
Exam-prep question bank for medical licensing exams.
App Store
kfzteile24
Germany's leading online auto parts marketplace.
App Store
Cortado
Enterprise mobile device management and secure workplace access.
App Store
ThinPrint
Secure cloud and mobile printing for enterprise fleets.
App Store
TIGNUM QOT
Executive performance coaching for elite athletes & leaders.
App Store
M-sense
Migraine tracking & therapy companion (Newsenselab).
Delisted
Featured Work
Behind the products
The engineering underneath the interfaces, with payments first and architecture, performance, quality, and platform work behind it.
Payments & FinTech
I’ve built the path from tap to settlement: tokenization, 3DS/SCA, wallets, BNPL, gift cards, top-ups, credits, corporate invoices, and rules that change from market to market.
30+
Payment methods
22
Providers
Architecture & Modular SDKs
I built one payment SDK that Wolt, DoorDash, and Deliveroo can ship without forking it. Clear protocol boundaries and dependency injection keep the shared code adaptable without hiding how it works.
3
Brands, one SDK
1
Shared codebase
Interface & Interaction Craft
I’ve shipped server-driven UI, custom bottom sheets, and motion tied to real design-system tokens. Entry and exit timings are tested separately because the details are visible in everyday use.
11
Apps shipped
Server
Driven UI
Performance & Reliability
I migrated payment modules to Swift 6 strict concurrency, added caching on hot paths, and used leak detection and distributed traces to find where time and memory were actually going.
Swift 6
Concurrency
PCI
Audit passed
Testing & Automation
I wired Maestro end-to-end tests into CI across three brands. I add characterization tests before risky refactors and investigate flaky tests instead of teaching the team to ignore them.
3
Brands covered
E2E
In CI
Platform & Design Systems
I work daily in Prism and Mosaic, large monorepos, Bazel and SPM builds, and staged feature rollouts. The platform work is successful when product teams can make changes without learning every internal detail first.
2
Design systems
3
Build systems
How card payment authorization works
Request, authentication, and approval across five systems
Authorization request
3-D Secure challenge
Approval response
Recognition
In their words
“We are delighted to work with such a forward-thinking group of people from Wolt to transform the way people check out.
Special thank yous to the amazing Team Wolt: … Aamir Suhial …”
R
Emma Pitt, Revolut
On the launch of Revolut Pay across Wolt • 20+ European markets
Live in
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“Aamir has taken excellent care of our iOS payments SDK. He played a central role in integrating ProcessOut,
helped us pass the PCI compliance check, and drove technical discussions through several RFCs.”
E
Emil Dodevski, Engineering Manager
Payments Platform, DoorDash / Wolt
Skills
Tools I trust
A deliberately small toolkit for building reliable iOS products.
Languages & Frameworks
Swift
UIKit
SwiftUI
Objective-C
Swift Concurrency
Architecture & Patterns
Clean Architecture
Modular SDK Design
Server-Driven UI
Dependency Injection
Feature Flags & Experimentation
Build & DevOps
Bazel
SPM
Bitrise
Fastlane
GitHub Actions
Testing & Observability
XCTest
Swift Testing
Maestro (E2E)
Memory Leak Detection
OpenTelemetry
Developer Tooling
Claude Code
OpenAI Codex
Cursor
MCP Servers
FinTech & Payments
3DS / SCA & PSD2
Tokenization & PCI DSS
Authorization, Capture & Idempotency
Wallets & Device Attestation
Gift Cards, Credits & Top-Ups
Corporate Invoicing
BNPL, Bank Redirects & SZÉP
Multi-Currency & Market Rules
Apple Pay · PayPal · Braintree
Adyen · Finaro · Stripe · Spreedly · ProcessOut
Education
University Projects
Foundations
2016 to 2019
Technische Universität Berlin
Computer Science: Distributed Systems & Software Engineering
2012 to 2014
Jamia Hamdard
Computer Science
2009 to 2011
University of Kashmir
Bachelor of Computer Applications
Privacy and Security: A Concern in Social Networks
Research Publication
TU Berlin: My journey into distributed systems
Blockchain, cloud infrastructure, and the projects that shaped how I think about software at scale.
Advanced Web Technologies
Blockchain Meets Media
A decentralised music distribution dApp on Ethereum. Solidity smart contracts handle ownership and
royalties, IPFS stores the audio as content-addressed hashes so no central server holds the catalogue,
and MetaMask signs transactions straight from the browser.
Solidity
Ethereum
Truffle
Ganache
IPFS
MetaMask
JavaScript
View repository
Elastic Computing
AWS Rekognition vs. Google Cloud Vision
A benchmark of two computer-vision APIs across face, label, text, and logo detection, scored on
completeness and correctness. Built the same pipeline four ways using Java, AWS Lambda serverless,
PHP, and Python. This let me compare the platforms fairly rather than trusting one SDK's ergonomics.
Python
Java
AWS Rekognition
Google Cloud Vision
AWS Lambda
Serverless
View repository
Cloud Infrastructure
Incident Management Chatbot
A TU Berlin team project that automated incident response across chat, voice, and monitoring systems.
We connected AWS Lex and Amazon Connect to Lambda, CloudWatch, and Prometheus Alertmanager so engineers
could inspect, escalate, and respond to an incident without watching a dashboard.
Terraform
Amazon Connect
AWS Lex
AWS Lambda
CloudWatch
Prometheus
View team repository
Research
Privacy and Security in Social Networks
A published paper examining how social platforms leak personal data through default visibility,
third-party access, and inference from public graphs. It also considers what privacy-preserving
alternatives actually cost in usability.
Privacy Engineering
Security
Published Paper
Contact
Let's solve something complex.
Open to thoughtful conversations about iOS architecture, FinTech, and product engineering at scale.
Get in touch
Have a project, opportunity, or difficult architecture problem? I’d be glad to hear about it.
Berlin
Germany