Software Engineer, Payment Interfaces

Since we opened our doors in 2009, the world of commerce has evolved immensely, and so has Square. After enabling anyone to take payments and never miss a sale, we saw sellers stymied by disparate, outmoded products and tools that wouldn’t work together.

So we expanded into software and started building integrated, omnichannel solutions – to help sellers sell online, manage inventory, offer buy now, pay later functionality, book appointments, engage loyal buyers, and hire and pay staff. Across it all, we’ve embedded financial services tools at the point of sale, so merchants can access a business loan and manage their cash flow in one place. Afterpay furthers our goal to provide omnichannel tools that unlock meaningful value and growth, enabling sellers to capture the next generation shopper, increase order sizes, and compete at a larger scale.

Today, we are a partner to sellers of all sizes – large, enterprise-scale businesses with complex operations, sellers just starting, as well as merchants who began selling with Square and have grown larger over time. As our sellers grow, so do our solutions. There is a massive opportunity in front of us. We’re building a significant, meaningful, and lasting business, and we are helping sellers worldwide do the same.

The Role

Payment Interfaces builds and operates the APIs and services that power payment experiences across Block, including Square, Cash App, and Afterpay. Our systems process payment traffic worldwide, helping sellers accept payments and customers move money reliably and securely.

You’ll design, build, and scale customer-facing payment APIs and the critical systems behind them. You’ll bring experience in payments, lead complex projects from design through production, and help shape the team’s technical direction. You’ll learn the specifics of Block’s products and payment processing on the job.

This is a hands-on engineering role with ongoing operational responsibility. Alongside building new capabilities, you’ll maintain high-volume production systems, participate in on-call and incident response, and make improvements that prevent recurring problems. You’ll use AI throughout your work while remaining accountable for the correctness, security, and reliability of what you ship.

You Will

• Design, build, maintain, and scale customer-facing payment APIs with clear contracts, predictable behavior, and compatibility that developers can rely on.
• Lead complex projects end to end: clarify requirements, evaluate trade-offs, plan incremental delivery, and own testing, rollout, and ongoing maintenance.
• Operate critical payment systems serving worldwide traffic. Participate in the team’s on-call rotation, investigate incidents, and follow through on fixes that improve reliability.
• Improve performance, observability, fault tolerance, and security. Use automation to reduce repetitive operational work and make systems safer to change.
• Work with product and engineering partners across Block to turn payment requirements into reusable capabilities.
• Use AI-assisted tools for design, implementation, testing, and debugging. Critically evaluate their output and help teammates adopt approaches that improve quality and delivery.
• Shape technical decisions within the team and develop others through design reviews, code reviews, documentation, and mentoring

You Have

• Experience building, maintaining, and scaling customer-facing financial or payment APIs, together with a strong understanding of payments. This is a requirement for the role.
• Experience designing and operating high-volume, highly available distributed systems where correctness, security, and reliability matter.
• An understanding of payment API concerns such as idempotency, retries, asynchronous processing, backward compatibility, and handling partial failures without compromising financial correctness.
• A record of leading complex engineering projects from unclear requirements through production, making technical trade-offs, and coordinating work with partner teams.
• Experience diagnosing production issues and improving systems through monitoring, incident response, and preventive engineering.
• Fluency with AI-assisted engineering tools and the judgment to validate generated code, protect sensitive data, and recognize when deeper investigation is needed.
• Clear written communication and experience helping other engineers develop their technical skills.
• A minimum of 8 years of related experience with a Bachelor’s degree; or 6 years and a Master’s degree; or a PhD with 3 years experience; or equivalent experience

Technologies We Use and Teach

• Kotlin
• Go
• TypeScript
• AWS
• Kafka

We’re working to build a more inclusive economy where our customers have equal access to opportunity, and we strive to live by these same values in building our workplace. Block is an equal opportunity employer evaluating all employees and job applicants without regard to identity or any legally protected class. We will consider qualified applicants with arrest or conviction records for employment in accordance with state and local laws and “fair chance” ordinances.

We believe in being fair, and are committed to an inclusive interview experience, including providing reasonable accommodations to disabled applicants throughout the recruitment process. We encourage applicants to share any needed accommodations with their recruiter, who will treat these requests as confidentially as possible. Want to learn more about what we’re doing to build a workplace that is fair and square? Check out our I+D page.

While there is no specific deadline to apply for this role, U.S. roles are typically open for an average of 55 days before being filled by a successful candidate. Please refer to the date listed at the top of this job page for when this role was first posted.