Senior Kotlin Developer

Description

We are looking for a Senior Kotlin Developer to join the core of our financial API gateway — a mission-critical platform that mediates communication between ERPs and financial institutions, processing real transactions with high reliability, security, and availability. We seek a hands-on, analytical profile who develops autonomously and adds value to the team by deeply understanding business problems, collaborating closely with Product, and proactively identifying gaps. **Responsibilities and duties** * Develop and evolve Kotlin microservices with a focus on robustness, performance, and scalability. * Implement end-to-end integrations with financial institution APIs — interpreting bank manuals and technical specifications, and translating them into reliable solutions. * Design domain-driven solutions (DDD) and manage inter-service communication (REST and events). * Act as a Product partner, contributing technical perspective to refine requirements and anticipate gaps. * Ensure security, observability, and reliability from the design phase; participate in code reviews and production incident resolution. **Requirements and qualifications** * 5+ years of JVM development experience, with solid, proven expertise in idiomatic Kotlin. * Microservice architecture and inter-service communication. * Integration fundamentals: REST and SOAP APIs, deep HTTP knowledge (status codes, headers, idempotency, retry), authentication (OAuth2, mTLS, payload signing), digital certificates, and queues/messaging. * Ability to independently interpret third-party documentation and specifications (APIs, banking manuals) and implement them autonomously. * Strong foundation in DDD, Clean Code, and SOLID; relational databases (PostgreSQL). * Excellent analytical ability and strong technical communication skills for a remote team. Nice-to-have * Applied AI in development (assistants, agents, analytical support) — we use AI intensively in our workflow and highly value candidates who have already integrated it into their daily routine. * Prior experience with financial, banking, or payment systems. * Ktor, event-driven architecture, automated testing, CI/CD, and cloud (Azure/AKS, Kubernetes), API documentation (OpenAPI). **Additional information** Check out our benefits: Totalpass for your physical and mental well-being. Psychological support program. Equipment provided by the company. Day OFF. Referral bonus for professionals you recommend. **About eSales** With 30 years in the market, we are a company committed to simplifying communication and relationships between businesses, generating valuable connections to transform organizations. **What we do?** The eSales Group is now a technology ecosystem offering specialized solutions across multiple segments, including **logistics, supply chain, demand forecasting, sales intelligence, financial integrations** (payments and collections), and **electronic data interchange**. With market-proven platforms and a focus on high performance, we serve **major clients across Brazil**, including **public sector entities, industrial companies, and retailers**. Our strategic involvement helps organizations become more efficient, connected, and prepared for future challenges. **A Great Place to Work-certified company** Our culture’s excellence is also officially recognized: we have been certified by **Great Place to Work (GPTW)** for **six consecutive years** — 2020, 2021, 2022, 2023, 2024, and 2025! This recognition reflects our daily commitment to the well-being, development, and appreciation of every person who contributes to our story. Here, our values guide every action, decision, and achievement.