Staff Software Engineer, Square Cards

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
Square helps business owners access, manage, and grow their money. The Square Debit Card is at the center of that experience - a business card sellers use every day to pay vendors, manage cash flow, and reinvest in their business. The Cards team owns the entire cardholder journey, from activation and digital wallet integration to spend incentives and rewards. We're building systems that help sellers trust Square with more of their financial lives.
We're looking for a Staff Product Engineer to shape the next generation of our card experience. You'll lead technical strategy for how we personalize and optimize key seller moments - using data, experimentation, and ML to help sellers get value from Square faster and keep them engaged longer. This is a hands-on, cross-functional role: you'll work closely with PMs, data scientists, and ML engineers to build, measure, and iterate on new product hypotheses at scale.
What you'll do

• Lead design and development of systems that drive seller engagement through incentives, onboarding, and spend experiences.
• Build and scale experimentation frameworks for testing offers, activation flows, and cardholder behaviors across millions of users.
• Partner with ML teams to integrate models that predict engagement and personalize incentives, rewards, or educational nudges.
• Develop infrastructure and pipelines that enable fast iteration and statistically sound decision-making.
• Collaborate with design, product, and analytics to translate insights into production features that improve retention and satisfaction.
• Mentor engineers across teams, raising the bar for experimentation quality, observability, and data-driven development.
• Set technical direction for how the Cards team measures, learns, and ships product changes efficiently and responsibly.

You have

• 12+ years of engineering experience, including deep work in product-facing or ML-enabled systems.
• A strong background in backend or full-stack development using languages like Java, Kotlin, Ruby, Go, or Python.
• Experience building large-scale experimentation or personalization systems (A/B testing, feature flagging, model integration).
• Familiarity with modern ML workflows - e.g., training/inference pipelines, feature stores, or real-time scoring - and how to integrate them safely into production systems.
• A track record of influencing product direction through data and experimentation, not just intuition.
• Strong collaboration and communication skills; able to bridge engineering, product, and data to ship measurable impact.
• Comfort working in tier 0 critical environments where accuracy and trust matter.

Technologies we use

• Backend: Java, Kotlin, Go, Ruby on Rails
• Data & ML: Python, Airflow, Spark, Snowflake, TensorFlow, Databricks
• Infra: Kubernetes, AWS, Terraform, Protocol Buffers, Temporal

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 .
Block takes a market-based approach to pay, and pay may vary depending on your location. U.S. locations are categorized into one of four zones based on a cost of labor index for that geographic area. The successful candidate's starting pay will be determined based on job-related skills, experience, qualifications, work location, and market conditions. These ranges may be modified in the future.
To find a location's zone designation, please refer to this resource . If a location of interest is not listed, please speak with a recruiter for additional information.
Zone A:
$263,600 - $395,400 USD
Zone B:
$263,600 - $395,400 USD
Zone C:
$263,600 - $395,400 USD
Zone D:
$263,600 - $395,400 USD
Use of AI in Our Hiring Process
We may use automated AI tools to evaluate job applications for efficiency and consistency. These tools comply with local regulations, including bias audits, and we handle all personal data in accordance with state and local privacy laws.
Contact us at [email protected] with hiring practice or data usage questions.
Every benefit we offer is designed with one goal: empowering you to do the best work of your career while building the life you want. Remote work, medical insurance, flexible time off, retirement savings plans, and modern family planning are just some of our offering. Check out our other benefits at Block.
Block, Inc. (NYSE: XYZ) builds technology to increase access to the global economy. Each of our brands unlocks different aspects of the economy for more people. Square makes commerce and financial services accessible to sellers. Cash App is the easy way to spend, send, and store money. Afterpay is transforming the way customers manage their spending over time. TIDAL is a music platform that empowers artists to thrive as entrepreneurs. Bitkey is a simple self-custody wallet built for bitcoin. Proto is a suite of bitcoin mining products and services. Together, we're helping build a financial system that is open to everyone.