Software Engineer, Backend Developer

KAYAK, part of Booking Holdings (NASDAQ: BKNG), is a leading travel search engine. With billions of queries across our platforms, we help people find their perfect flight, stay, rental car and vacation package. We're also transforming business travel with a new corporate travel solution, KAYAK for Business.

As an employee of KAYAK, you will be part of a travel company that operates a portfolio of global metasearch brands including momondo, Cheap flights and Hotels Combined, among others. From start-up to industry leader, innovation is in our DNA and every employee has an opportunity to make their mark. Our focus is on building the best travel search engine to make it easier for everyone to experience the world.

KAYAK is seeking a Senior Java Software Engineer to join our Retention and CRM team! The Retention team powers the backend systems behind our Trips product and builds features that keep travelers coming back to KAYAK again and again. The CRM team designs and scales the platform behind personalized email and push notifications delivered to millions of users. In this role, you'll collaborate with engineers, product managers, and marketing specialists to build meaningful, high-impact experiences across both areas.

This role is required to work from either our Cambridge or Concord, MA office 3 days per week.

• Design and deliver scalable, high-quality backend services across both Retention and CRM — including systems that power the Trips product, user re-engagement features, and large-scale email and push notification pipelines.

• Develop and improve backend services handling bulk and transactional messaging at scale, ensuring reliability and performance across millions of sends.

• Build and maintain backend features that drive user retention — including Trips functionality, price alerts, and personalized engagement touchpoints that bring travelers back to KAYAK.

• Architect and maintain robust integrations with third-party APIs and marketing platforms, ensuring data integrity and scalability across the email and retention stack.

• Lead the design of complex features end-to-end — from technical scoping and architecture decisions through deployment, monitoring, and production support.

• Collaborate with cross-functional teams including product managers, marketing specialists, designers, and globally distributed engineers to translate business requirements into well-engineered solutions.

• Debug and optimize full-stack solutions, proactively identifying performance bottlenecks, data pipeline failures, and production issues — and driving them to resolution.

• Contribute to engineering excellence by upholding coding standards, PR review practices, and operational monitoring, including alerting and incident response for team-owned systems.

• Coach and mentor junior and mid-level engineers through code reviews, design discussions, and knowledge sharing, helping to raise the technical bar for the team.

• Explore and apply emerging technologies — including AI-assisted tooling and automation — to improve developer productivity, personalization, and platform capabilities.

• Strong, proven programming skills in Java, with the ability to independently design, implement, and own complex backend features end to end.

• Solid experience with APIs and SQL — including designing and consuming RESTful APIs and working with relational databases such as MySQL or similar systems.

• 5+ years of professional software engineering experience, with a track record of delivering high-quality, production-grade backend systems in a fast-paced environment.

• Experience leading the design and delivery of complex technical solutions, including making architectural tradeoffs and owning features through deployment and ongoing operations.

• Experience collaborating cross-functionally with product managers, marketing partners, designers, and globally distributed engineering teams to ship impactful features.

• A collaborative mindset and openness to learning and sharing ideas, including a willingness to mentor others through code reviews and knowledge sharing.

• Ability to manage multiple priorities and adapt to changing needs without requiring…