Senior Backend Engineer at Casavo

The Role: Building a Solid Foundation We are currently migrating our core systems from a legacy Scala monolith to a modern Kotlin Modular Monolith. You will join our backend team to help us safely extract business domains from the old system and rebuild them in Kotlin, applying Domain-Driven Design (DDD) with a practical, hands-on approach. While your primary focus is the core engine for our agents, you will not be working in a silo. You will design integrations and event-driven flows to communicate with Casavo’s broader ecosystem of backend [micro]services (e.g., consumer platforms, data warehouses, and identity providers). We are also preparing our platform for the future. As we scale, our APIs won't just be consumed by frontend applications, but increasingly by autonomous AI tools and automations. Because of this, we care deeply about building robust, predictable, and well-documented APIs. If you enjoy writing clean code, optimizing SQL queries, and shipping reliable software without over-engineering it, you’ll fit right in. Our Tech Stack • The New Core: Kotlin (Coroutines), Ktor / Http4k, Gradle Multi-module. • The Legacy (to be migrated): Scala, MySQL. • The Database: PostgreSQL (focused on efficient querying and keyset pagination). • Infrastructure & Comms: RabbitMQ, In-Memory Event Buses, Docker, AWS, k8s, GitHub.Key Responsibilities • Develop the Modular Monolith: Write clean, maintainable Kotlin code for our new backend services, ensuring clear boundaries between business domains. • Migrate and Modernize: Work alongside the team to understand existing business logic in the Scala monolith and rewrite it in the new Kotlin architecture with zero downtime. • Cross-System Integration: ensure smooth communication between the core system and other Casavo services. • Build Robust, AI-Ready APIs: Design predictable REST APIs. You'll implement standard error formats (RFC 7807), strict OpenAPI specs, and safe pagination (cursors) so our endpoints are rock-solid for both human UIs and future Machine-to-Machine/AI integrations. • Database & Performance: Design relational database schemas (PostgreSQL) and write efficient SQL queries that scale gracefully as our data grows. • Collaborate & Deliver: Work closely with frontend developers, product managers, and the rest of the engineering team to ship features iteratively and reliably.