Contract Principal Software Engineer (Java Spring)

About the Company:

Stable Kernel is a technology services firm and custom software developer building scalable software solutions for cutting-edge, innovative enterprises to move their business forward. We are headquartered in Atlanta, GA.

We’re a privately held, Great Place to Work Certified Company™ with a multi-award-winning culture and an impressive 10-plus-year trajectory of sustainable growth. At Stable Kernel, we support our employees in ways that help them do some of the best work of their lives.

About the Role:

As a Stable Kernel Contract Principal Software Engineer, you play an essential role in setting our portfolio of world-class clients up for success through the development and delivery of their most innovative, transformational initiatives. You will collaborate daily with other engineers and product team members, make decisions that influence the path of a product roadmap, leverage software development best practices, and become a more well-rounded engineer as you learn new technologies. Your knowledgeable practice, reliability, and consultative nature make you an engineer that stakeholders and teammates trust.

Core Responsibilities Include:

• Technical Impact: 
• Design and implement loyalty engine services in Java using the Spring framework, including transaction processing, tier calculation, reward accrual, and benefit eligibility.
• Design and implement RESTful API services in Java using the Spring framework, following contract-first development practices, with a focus on aggregation patterns, caching strategies, circuit breaking, and graceful degradation for latency-sensitive flows.
• Modern Java (17+) and familiarity with current Spring Boot conventions, including reactive patterns where appropriate.
• Cloud platform experience (AWS, GCP, or Azure), including service deployment, networking fundamentals, and managed services such as queues, caches, and databases.
• Identity and access management protocols such as OAuth 2.0, OIDC, and SAML, including integration with enterprise identity providers and directory services.
• Establishing and evolving service architecture, including domain modeling, rules evaluation patterns, event-driven state management, auditability, API versioning, and backward-compatibility standards that support independent mobile release cadences.
• Defining integration contracts with upstream enterprise platforms (POS, CRM, commerce, identity providers) and downstream consumers (BFF, analytics, finance), including data normalization, error mapping, and retry logic.
• Building and maintaining integrations that pull transaction data from multiple channels and apply consistent earning logic regardless of source.
• Authentication and session management patterns, including token refresh, device trust, and silent re-authentication for long-lived mobile sessions.
• Implementing cross-cutting concerns such as idempotency, correlation IDs, observability, and audit event emission.
• Implementing robust state management for account-level aggregations, provisional and finalized reward states, and period-based accrual tracking.
• Designing test strategies for complex business rules, including edge cases around split-tier earning, return adjustments, forward offsets, delegate activity aggregation, and high system reliability.
• Implementing security and audit concerns: role-based access, 2FA for redemption flows, full audit trails for all state changes.
• Designing and involving yourself in CI/CD and automated testing for high system reliability.
• Providing expert feedback that improves the overall delivery of work and ensuring a high standard of quality across the project.
• Using AI-assisted development tools such as Claude Code or Cursor to accelerate delivery while maintaining code quality and architectural standards.
• Business Alignment: 
• Clarifying strategic outcomes and influencing roadmaps and projects.
• Identifying, suggesting, and driving improvements in your customers' end-to-end experience.
• Aiding in estimating work for new business with more unknowns and coaching others in estimation best practices. 
• Interacting with Others: 
• Coordinating across the entire company.
• Influencing the entire organization to make changes to support your work.
• Advising teams across the company.
• Autonomy & Ambiguity: 
• Designing a long-term roadmap with no direction. 
• Translating customer and business needs and strategic direction into projects and consistently simplifying high-complexity situations.
• Coaching and mentoring others in tackling ambiguity.
• Problem-Solving:
• Decomposing strategic direction into projects:
•  Planning, communicating, and executing to solve our most challenging problems.
• Ensuring alignment with long-term objectives, fostering a culture of informed decision-making and innovation.
• Anticipating most risks and driving simplification to mitigate risks ahead of time. 
• Escalating issues while solving them in parallel ensuring others are informed.
• Leadership:
• Proposing new organization-level processes to improve key areas such as team throughput, employee happiness, or product engagement.
• Driving best practices across the organization.
• Exhibiting exceptional mentoring abilities and fostering a culture of continuous learning and improvement by
• identifying and nurturing potential in others 
• providing strategic guidance
• helping develop career paths for team members 
• Leading projects.
• Setting the strategic direction for projects or areas of technology, leading multiple project teams, and influencing decision-making at higher organizational levels. 
• Exhibiting strong capabilities in stakeholder management, negotiating, and problem-solving in complex scenarios. 
• Mentoring and developing other leaders within the team, fostering a culture of innovation, and contributing significantly to organizational goals.

Deep Expertise With:

• Java for server-side development.
• The Spring framework ecosystem (Spring Boot, Spring MVC, Spring Security, Spring Data).
• Domain-driven design principles, including bounded contexts, aggregates, and domain events.
• RESTful API design principles, including contract-first approaches and OpenAPI/Swagger.
• Event-driven and message-oriented patterns (e.g., Kafka, RabbitMQ, or SQS) for reliable state transitions and integration.
• Integration patterns: API gateway, circuit breaker, retry/backoff, caching (Redis or similar), ETL or event-based data flows, and idempotency.
• Relational databases (e.g., PostgreSQL, MySQL) with strong skills in schema design, query optimization, and transactional integrity; familiarity with NoSQL datastores a plus.
• Rules engine patterns or configurable business logic frameworks.
• CI/CD tooling such as Jenkins, GitHub Actions, or similar, including pipeline authoring and deployment automation.
• Containerization and orchestration tools such as Docker and Kubernetes.
• SCM tools such as Git.
• Observability tooling such as Datadog, Splunk, New Relic, or OpenTelemetry.
• Automated testing at multiple layers: unit (JUnit, Mockito), integration, contract testing, and scenario-based validation of business rules.

General Requirements:

• 10+ years of development experience with an emphasis on back-end development. 
• Extensive experience serving as a trusted consultant to stakeholders and cross-functional teams, providing expert guidance on backend service design, delivery, and integration.
• Degree in Computer Science or relevant field or experience. 

Nice to Haves:

• Experience building loyalty, rewards, or financial calculation engines.
• Experience building BFF or API aggregation layers for mobile applications.
• Familiarity with Salesforce CRM, Commerce Cloud, or Identity integration patterns.
• Experience with POS system integration and transaction-level data processing.
• Background in fintech, payments, or systems where auditability and financial accuracy are critical.
• Experience modeling complex account hierarchies (parent-child organizations, delegate/role structures).
• Experience with feature flagging and progressive rollout.
• Experience working alongside mobile teams to negotiate and iterate on API contracts.

A Bit More Info:

Minimum Base Compensation: $105

This is a contract position.

Stable Kernel operates a People Before Place Hybrid model, allowing most employees to choose where they can do their best work most days.

Minimal travel is associated with this role.

*Note – We are not sponsoring employment visas at this time. If you are currently in possession of an employment visa, it will need to be effective for at least 3 years from the date of your application for your candidacy for employment to be considered.

Stable Kernel’s culture is inclusive and expansive. We celebrate diversity in its many glorious forms and do not discriminate based on race, religion, color, national origin, gender role orientation, sexual orientation, age, marital status, veteran status, or disability status.

However, we will discriminate against those unwilling to comply with the practice of our company values:

• we work with integrity always
• we respect our work and each other
• we are dedicated to life-long learning and sharing
• we stay hungry for new challenges

If you are like-minded in this regard, we hope you will apply. We look forward to meeting you.