Senior Staff Software Engineer, Partner Integrations

Flex is a growth-stage, NYC headquartered FinTech company that is creating the best rent payment experience. It’s hard to believe that it’s 2026 and paying rent on time is expensive, inflexible, and difficult. We’re here to change that! Flex enables our users to pay rent throughout the month on a schedule that better fits their finances and budget. Our mission is to empower as many renters as possible with flexibility over their most significant recurring expense. After deliberately keeping a stealth profile as we built up unprecedented investor support and an enthusiastic user base, we are looking for motivated individuals to help us keep our mission growing. Will you be a part of the team?

Flex exists to make paying rent work the way real life actually works — smoothing out cash flow, helping renters avoid late fees, and letting them build credit instead of falling behind. As a Senior Staff Backend Engineer, you'll oversee the technical roadmap for the team, working across APIs, SDKs, and Web experiences. You will work with teams across the organization including Engineering, Product, Design, Infrastructure, Sales, Partner and Customer Success to ensure that the technical strategy meets our goals. We expect you to be hands-on and execute work as an individual, and build products that allow for flexibility as we evolve our product offerings.

About Our Team!

We have some really exciting teams who are looking for an amazing engineer like you! Check them out!

• Partner Integrations - Partner integrations work to standardize APIs, tools, and processes that let external partners connect to Flex for data sharing and payments across entry points like Flex Anywhere

Who thrives here?

• A Doer — you get things done efficiently, and you're comfortable rolling up your sleeves when something's blocking the team.

• An Owner — you take full accountability for what you build, from design through production, and you always have a plan B.

• Someone Collaborative — you bring people together to pressure-test ideas rather than working in a silo.

• Someone with Precision — your code and your communication are both clear, because ideas only matter once others can act on them.

• Someone Resilient — systems break and priorities shift, and you adapt without losing momentum.

• Someone Humble — you care more about getting to the right answer than being the one who's right.

• Bachelor or above degree in Computer Science or a related field

• Minimum of 10 years experience in software engineering, with at least 3 years of technical leadership experience in a hands-on capacity

• Ability to work on a globally-distributed team with a high degree of ownership

• Experience leading the delivery of multiple highly impactful products end to end, on time with a high quality bar

• Experience working with technical and non-technical stakeholders, successfully aligning and setting expectations on scope and delivery

• Ability to drive yourself and your team to bring quality and consistency to their code and architecture, without compromising velocity

• Ability to grow in a fast-paced and dynamic environment that will challenge you to always bring your best

• Experience in designing and developing solutions that maximize ROI and lead to significant business impact

• Experience working in FinTech and familiar with major payment rails

• Experience working with Sales stakeholders and/or building products for Sales professionals

• Experience building integrations with external partners &