Senior iOS Engineer

About Knot Knot's mission is to empower consumers and businesses alike with connected merchant and banking experiences. Knot is like "Plaid for merchant connectivity." We are building the platform connecting merchants to the many applications that consumers and businesses interact with everyday. Our flagship CardSwitcher product allows consumers to instantly update & manage their cards on file with online merchant accounts (e.g. Netflix or PayPal), while newer products like TransactionLink support the retrieval of receipt-level transaction data and AgenticShopping enables 1-click, native shopping experiences. Founded in 2021, Knot was founded by two brothers and Thiel Fellows - Rory and Kieran O'Reilly - and today powers connected online payment experiences for hundreds of thousands of consumers. Companies like American Express, PayPal, Current, BILT, Step, and more choose to embed Knot's SDK in their apps to power best-in-class experiences for their customers. Knot is proudly backed by a select group of investors, including Nava Ventures, 8VC, American Express, Plaid, and co-founders & CEOs of prominent companies like Twitter, Warby Parker, Allbirds, Casper, Intercom, Deel, Italic, DraftKings, and many more. About the role We are looking for a Senior iOS Engineer to help shape the architecture, reliability, and performance of our SDK, which powers mission-critical experiences for some of the largest FinTechs in the world. You will work across the entire lifecycle of our iOS SDK, from design to release. This includes shaping how we profile performance, how we catch issues before they ship, how we test our public APIs, and how we produce documentation that makes our SDK easy to integrate. You will collaborate with product and engineering teams across the company, and you will help represent and advocate for our SDK both internally and externally. What you'll be doing Lead and contribute to the architecture, design, and optimization of the iOS SDK Profile, debug, and improve memory usage, CPU consumption, concurrency, and overall runtime efficiency Design stable, predictable public APIs and produce documentation that supports developers integrating our SDK Strengthen test coverage with unit tests, UI automation, integration testing, and performance testing Co-own the mobile CI/CD workflows that ensure safe, reliable, and repeatable releases Investigate production issues with attention to detail and implement long-term safeguards Advocate internally and externally for best practices around integration, performance, and reliability Participate in cross-team technical planning and represent the platform's needs Evangelize the SDK and help educate teams on its capabilities and usage Contribute to building an engineering culture rooted in clarity, ownership, and thoughtful design What you'll need to get the job done Strong debugging skills and proficiency with native profiling tools Deep understanding of memory allocation, leaks, CPU usage, and asynchronous patterns Experience building asynchronous and multithreaded architectures Ability to design, validate, and document public SDK APIs Strong unit testing mindset and experience uncovering failure modes and edge cases Familiarity with mobile CI/CD pipelines and the desire to improve them Comfortable executing thorough QA validation prior to releases Clear and effective communication with cross-functional teams Experience writing and debugging UI automation tests Familiarity with feature flagging and controlled rollout strategies iOS Specific Skills Deep experience with WKWebView including navigation, messaging, resource handling, and hybrid debugging Proficiency with Swift and Swift Concurrency Experience with ARC, Instruments, and iOS frameworks Experience building and maintaining frameworks or Swift Packages Familiarity with Xcode build tooling and performance optimization What we offer Interesting and challenging work Competitive base salary + up to 20% annual bonus + generous early employee equity + benefits 100% medical, dental, and vision insurance coverage for you and your dependents (U.S.) Unlimited PTO Parental leave Beautiful NYC office in the heart of Flatiron Herman Miller Aeron desk chair Food (snacks, frequent lunches & often dinner for those working late) Knot