Full-stack Engineer (Java+React.js)

Limestone Digital; Central (LA); On-site; USD 120,000 - 160,000; Full time

Job summary

Limestone Digital is seeking an experienced backend engineer to join our payments and loyalty platform. You will work with Java 17/21, Spring Boot microservices, Kafka, MongoDB, Redis, and Docker/Kubernetes.

You will deliver internal dashboards with React/TypeScript, integrate with external providers via REST and signatures, and apply AI-assisted tooling to accelerate delivery.

The role emphasizes reliability, testing, and performance as the platform scales to new brands and markets.

Qualifications

• Strong production experience with Java 17/21 and Spring Boot in microservices.
• Event-driven design using Apache Kafka, MongoDB / Amazon DocumentDB, and Redis (caching and distributed locks).
• Working knowledge of React with TypeScript for back-office interfaces and internal dashboards.

Responsibilities

• Build and support Java/Spring Boot services for payment processing, wallet mechanics, player modules, and bonus workflows.
• Deliver and refine operational and back-office dashboards using React with TypeScript.

Tools

Java

Spring Boot

Apache Kafka

MongoDB

Amazon DocumentDB

Redis

React

TypeScript

REST API

Docker

Kubernetes

GitLab CI/CD

Cursor

Claude

GitHub Copilot

NestJS

SingleStore

Analytical Databases

Job description

• Core Technology Stack: Strong production expertise with Java (17/21) and Spring Boot in microservices architectures.
• Messaging & Data Layer: Hands-on experience with event-driven design using Apache Kafka, MongoDB / Amazon DocumentDB, and Redis (caching and distributed locks).
• Frontend & Tooling: Working knowledge of React with TypeScript for back-office interfaces and internal dashboards.
• Integrations & Security: Proficiency in REST API design and external provider integrations (callbacks, digital signatures, HMAC).
• Testing & Infrastructure: Solid experience with Spring Boot test tooling for integration testing, alongside Docker, Kubernetes basics, and GitLab CI/CD pipelines.
• AI-Augmented Engineering: Daily hands-on practice with AI coding tools (Cursor, Claude, GitHub Copilot, or similar) to accelerate delivery.

Role Scope & Requirements

• Core Technology Stack: Strong production expertise with Java (17/21) and Spring Boot in microservices architectures.
• Messaging & Data Layer: Hands-on experience with event-driven design using Apache Kafka, MongoDB / Amazon DocumentDB, and Redis (caching and distributed locks).
• Frontend & Tooling: Working knowledge of React with TypeScript for back-office interfaces and internal dashboards.
• Integrations & Security: Proficiency in REST API design and external provider integrations (callbacks, digital signatures, HMAC).
• Testing & Infrastructure: Solid experience with Spring Boot test tooling for integration testing, alongside Docker, Kubernetes basics, and GitLab CI/CD pipelines.
• AI-Augmented Engineering: Daily hands-on practice with AI coding tools (Cursor, Claude, GitHub Copilot, or similar) to accelerate delivery.

Nice-to-Have Experience

• Domain knowledge in FinTech (PSP integrations, digital wallets, bonus engine mechanics, fraud/KYC flows).
• Performance optimisation (JVM tuning, MongoDB query optimisation) and load testing using Gatling.
• Secondary technology exposure: Node.js (NestJS), SingleStore, or analytical databases.

Key Responsibilities

• Service Development: Build and support Java/Spring Boot services for payment processing, wallet mechanics, player modules, and bonus workflows.
• Internal Dashboards: Deliver and refine related operational and back-office screens using React with TypeScript.
• External Integrations: Integrate, maintain, and optimise third-party payment providers and game aggregators.
• System Reliability: Enhance financial transaction systems with a focus on latency, resilient error handling, retry strategies, and idempotency.
• Quality & Verification: Maintain high code quality through unit/integration test coverage and participation in technical code reviews.
• Process & AI Efficiency: Leverage modern AI-assisted engineering practices to streamline implementation, reduce manual operational work, and support overall project goals.

Project Overview

The platform handles real-time player operations, payments, bonuses, and loyalty systems, while serving internal teams for compliance, risk, CRM, and analytics. As the platform scales into new markets and launches additional brands, our consultants collaborate directly with the client’s project teams to strengthen delivery capacity, elevate system reliability and performance, and replace manual processes through automation and AI-assisted engineering practices.