Senior Java Engineer

!!! Location: only Poland !!!

Who we are:

Adaptiq is a technology hub specializing in building, scaling, and supporting R&D teams for high-end, fast-growing product companies in a wide range of industries.

About the Product:

Our client is a major online gaming operator building a next-generation transactional platform for user account management. This is a greenfield project designed to operate in a highly regulated, high-volume environment and support millions of concurrent users. The platform will process financial transactions in real time and must ensure high availability, sub-second performance, data integrity, security, and full auditability. One of the key engineering challenges is maintaining reliability and performance during extreme traffic spikes and peak events.

The team is looking for strong technical expertise to help design and build a scalable, high-performance, and reliable backend platform that can meet strict security, regulatory, and compliance requirements.

About the Role:

As a Senior Java Engineer, you will design and build the core backend services of the PAM platform from the ground up. You will own features end-to-end, from technical design and implementation to automated testing, production monitoring, and release. You will work closely with Principal Engineers on architecture and technical decisions, contribute to RFCs, and deliver production-ready code. You will have a high level of autonomy and real influence over the platform’s design, while taking strong ownership of reliability, performance, and correctness in a critical financial system.

Key Responsibilities:

Design and build backend services in Java 17+ (Spring Boot or similar) for wallet transactions, ledger entries, payment orchestration, bonus mechanics, and account state management.
Develop REST APIs and event-driven integrations using Kafka or similar technologies for player-facing frontends, operations tooling, and external partners.
Ensure correctness and reliability through idempotent operations, clear transaction boundaries, explicit failure handling, and strong unit, integration, and contract testing.
Embed regulatory requirements into the platform, including KYC/AML checks, responsible gaming controls, and audit trails.
Ensure production readiness with metrics, structured logging, distributed tracing, alerting, and participation in on-call rotations.
Contribute to technical design and RFCs, participate in code reviews, and mentor other engineers.
Use AI-assisted development tools as part of the daily workflow, following platform standards for context and prompts.
Support live migration from the existing third-party platform, including parity testing, data validation, and cutover coordination.

Required Competence and Skills:

5+ years of backend engineering experience with strong hands-on expertise in Java 17+ and a modern framework such as Spring Boot.
Proven experience building and operating high-integrity transactional systems such as payments, wallets, billing, banking, e-commerce, or gaming.
Strong relational database expertise (PostgreSQL or equivalent), including schema design, ACID transactions, locking, and performance tuning.
Experience with event-driven architecture and messaging (Kafka, RabbitMQ, or similar), including idempotency and retry mechanisms.
Strong testing practices, including automated unit, integration, and contract tests as part of the standard development process.
Hands-on production experience with containers, CI/CD pipelines, monitoring/telemetry, and production incident troubleshooting.
Solid understanding of multi-threading, system architecture, and fault-tolerant design patterns.
Good written and spoken English, with experience working effectively in distributed, multi-time-zone teams.

Nice to Have:

Experience in iGaming, sports betting, fintech, or another regulated, high-transaction-volume domain.
Exposure to Kubernetes and AWS, including VPC, IAM, EKS, and auto-scaling.
Experience with compliance-driven development, including KYC/AML, responsible gaming, and audit requirements.
Experience with AI coding assistants and agentic development workflows.
Polish and/or Spanish language skills.

Why Us:
We provide 20 days of vacation leave per calendar year (plus official national holidays of a country you are based in).
We provide full accounting and legal support in all countries we operate.
We utilize a fully remote work model with a powerful workstation and co-working space in case you need it.