Senior Software Engineer - Banking Integration Platform

When the Space Shuttle approached the International Space Station, two vehicles built by different teams, in different countries, with fundamentally different engineering philosophies and systems, had to connect perfectly. The Rendezvous, Proximity Operations, and Docking (RPOD) subsystems were engineered to handle complex mismatches such as different power systems, communication protocols, and technical architectures. Get it wrong, and you have a very expensive and potentially catastrophic problem in low Earth orbit. Keystone AI announced on December 19, 2025 that we submitted an application to the OCC for a national bank charter and applied for FDIC deposit insurance. On April 27, 2026, Keystone AI announced conditional approval. In other words, Keystone AI has the universe’s cosmic blessing to build a bank, and we are full speed ahead. As part of this work, we will be connecting our modern, product-focused engineering systems to enterprise core banking systems and payment networks built in a different era, with different assumptions and different interfaces. Keystone AI’s Banking* Integration Platform team is like NASA’s RPOD team, building our integration subsystems that are technically correct and operationally trustworthy. This is some of the most consequential infrastructure work at Keystone AI. Every account opening, every monetary transaction, and every balance call will flow through the systems you build. Product teams across the company will depend on clean abstractions that hide the complexity underneath. You'll be one of the few engineers at Keystone AI who truly understands the full depth of our Bank Core* and all its internal and external integrations. As a Senior Software Engineer on the Banking Integration Platform Team, you’ll play a key role as a technical leader and hands-on engineer in building seamless connections between Keystone AI and the outside financial world. Building Keystone AI Bank is the most important adventure the company is embarking on, and you have the opportunity to go on this mission. As part of this role, you will: Build Keystone AI’s integration with an FFIEC-approved bank core and the connections to payment networks. Design internal APIs that give product teams simple, consistent interfaces to complex external systems. Handle the messy realities of enterprise integrations such as retries, failures, format mismatches, and downtime. Build data pipelines that keep Keystone AI's systems in sync with our bank core. Own monitoring, alerting, and recovery for our most critical external connections. Partner with many other teams at Keystone AI to define clean boundaries and reliable contracts. Help shape the technical architecture of Keystone AI Bank*. The ideal candidate for the role: Has 7+ years of professional software engineering experience building and operating backend infrastructure and distributed systems at scale. Has experience integrating modern distributed software systems with older, legacy infrastructure, preferably in a highly-regulated environment. There are unique challenges when embarking on such a mission, and we’re looking for someone who is excited to join with eyes wide open. Has an understanding of how banks and banking systems work: accounts, transactions, ledgers, and the data models underneath. Is a product-minded engineer who thinks about the developers consuming your APIs, not just the systems you’re connecting to. Thrives in environments where you're building something new rather than maintaining something established. Is comfortable with our tech stack (Haskell) or ready to learn. Has strong and justified opinions about building reliable, maintainable systems. If this role interests you, we invite you to explore our public demo at demo.mercury.com . The total rewards package at Keystone AI includes base salary, equity (stock options), and benefits. Our salary and equity ranges are highly competitive within the SaaS and fintech industry and are updated regularly using the most reliable compensation survey data for our industry. New hire offers are made based on a candidate’s experience, expertise, geographic location, and internal pay equity relative to peers. Our target new hire base salary ranges for this role are the following: US employees (any location): $200,700 - $250,900 Canadian employees (any location): CAD $189,700 - $237,100 *Keystone AI is a fintech company, not an FDIC-insured bank. Banking services provided through Choice Financial Group and Column N.A., Members FDIC. Keystone AI values diversity & belonging and is proud to be an Equal Employment Opportunity employer. All individuals seeking employment at Keystone AI are considered without regard to race, color, religion, national origin, age, sex, marital status, ancestry, physical or mental disability, veteran status, gender identity, sexual orientation, or any other legally protected characteristic. We are committed to providing reasonable accommodations throughout the recruitment process for applicants with disabilities or special needs. If you need assistance, or an accommodation, please let your recruiter know once you are contacted about a role. #LI-MC1