HotelPage Service (HPS) is one of the busiest, most business-critical systems at Booking.com — originally built as a REST API with Protobufs for speed and structure. It was fast but rigid. As product demands grew and clients needed more flexibility, cracks began to show: over-fetching, unclear ownership, and slow iteration cycles. This talk shares our real-world journey of modernizing that stack with GraphQL — not just adopting it as a new interface, but transforming how teams design schemas, collaborate across domains, and scale under load. We’ll walk through how we evolved from a proto-backed monolith to a federated GraphQL architecture — improving performance, enabling resolver ownership, and making the schema reflect real product needs. Whether you're planning a GraphQL migration or scaling one across teams, this talk delivers actionable insights and hard-won lessons from operating at billions of requests per day. Attendees will gain: - Align schema design with client and product needs - Handle organisational complexity in federation - Avoid pitfalls like over-fetching and the N+1 trap - Drive resolver ownership and collaboration - Optimise execution paths under high traffic
Senior Software Engineer, Booking.com
Mansi Mittal is a Senior Software Engineer with 12 years of experience, including 6 years at Booking.com. She has designed and architected critical, high-scale systems and led the migration from REST + Protobuf to federated GraphQL for high-volume, business-critical services. Passionate about scalable architecture, she bridges product needs with elegant engineering solutions.
Join three transformative days of expert insights and innovation to shape the next decade of APIs!