Senior Full Stack Engineer (Java/React)

Summary
Join Aperia Solutions, a fast-growing FinTech and managed consultancy building B2B accounts payable and payments platforms. You'll join a mid-size, distributed team working across the full stack - from Terraform infrastructure to Spring Boot services to React interfaces and database migrations. Aperia serves banks, processors, payment facilitators, merchant service providers, ISOs, and government entities.
This role offers technical ownership, a collaborative culture, and opportunities to shape product and architecture.
Job Description
We're seeking a Senior Full Stack Developer (Java, React) comfortable across backend, frontend, and cloud/infrastructure. You'll design, build, and maintain secure, high-performance payment systems and integrations. The ideal candidate has strong Java/Spring Boot experience, React front-end skills, relational database expertise (MySQL/Postgres), messaging/event-driven architecture experience, and practical AWS and infrastructure-as-code exposure.
Testing discipline, API security (OAuth2/JWT), and familiarity with distributed tracing are important.
Core Responsibilities
Design, create, maintain, and optimize applications using Spring Boot (MVC and WebFlux), React, and the Microsoft/Java tech stack where applicable.
Translate business requirements into functional, secure, and scalable solutions.
Build and maintain APIs (REST), integrate messaging queues, and implement async/event-driven patterns.
Manage DB schema design and migrations for MySQL/PostgreSQL; optimize queries and performance.
Participate in infrastructure-as-code efforts (Terraform or equivalent) and deploy to multi-environment AWS (ECS, Lambda, RDS, S3, SSM).
Secure APIs using OAuth2/Spring Security with JWT and policy-based authorization.
Maintain, upgrade, and refactor existing codebases to improve efficiency and performance.
Write and maintain unit and integration tests (JUnit, Mockito), and support CI/CD and observability (OpenTelemetry/distributed tracing).
Collaborate with product, QA, and distributed engineering teams; participate in Agile sprints and code reviews.
Ensure error-free code that follows best practices, design patterns, and security standards.
Mentor peers, investigate and resolve production issues, and support continual improvement.
Functional Responsibilities
Work with Business Analysts and US-based stakeholders to clarify requirements.
Propose technical approaches and detailed implementation plans.
Implement daily tasks, investigate issues, and support team members to deliver high-quality work.
Perform unit and cross testing; document results.
Conduct technical research and internal training.
Other duties as assigned.
Required Technical Skills & Experience
Minimum 6 years hands-on experience with Java and Spring Boot (MVC and/or WebFlux/Reactor).
Strong experience with React, REST APIs, HTML5, CSS3, and Bootstrap-based responsive UI.
Solid experience with relational databases (MySQL, PostgreSQL): schema design, migrations, and performance tuning.
Experience with messaging systems (RabbitMQ, AWS SQS/SNS, or similar) and event-driven patterns.
Practical AWS experience (Lambda, ECS, S3, RDS, SSM).
Knowledge of OAuth2/Spring Security, JWT, and policy-based authorization.
Testing discipline with JUnit, Mockito, or similar frameworks.
Strong understanding of performance, security, best practices, and design patterns.
Experience with Web Services; familiarity with WCF or .NET is a plus but not required.
Desirable Experience (will separate you from the rest)
Fintech/payments domain knowledge (ACH, NACHA, reconciliation, FBO models).
Terraform or equivalent IaC and multi-environment infrastructure management.
Deep experience with reactive programming (Mono/Flux).
Observability experience: OpenTelemetry, distributed tracing, metrics, and logging.
Hands-on experience with multi-tier/layer distributed applications.
Comfortable working in Agile/Scrum environments and with distributed teams.
Strong communication skills.
Education or Certifications
Bachelor's Degree in Computer Science, Information Systems, or related field (or equivalent experience).
Job Type & Schedule
Full time
Monday to Friday
Remote (need to live in VN)
Benefits
Competitive Salary Package - Enjoy a rewarding income from day one.
Security from the Start - Full salary during probation plus complete social insurance coverage.
Premium Health Insurance - Comprehensive protection for you and your loved one (spouse/children).
Family-Friendly Benefits - Monthly childcare support to make parenting easier.
Generous Leave Policies - 15 days annual leave, 6 weeks paternity leave, and 10 days bereavement leave.
Active Lifestyle - Join our vibrant clubs: Football, Billiards, Badminton, and E-sports...