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Freelance Java Backend Developer Jobs in Claymont, DE

IntraEdge

Senior Java Engineer

Middletown, DE · On-site

$54 - $68.75/hr

Design, develop, and maintain scalable Java-based backend applications and microservices. * Build ... Collaborate with product owners, architects, QA, and DevOps teams to deliver high-quality software ...

Collabera

Java Developer

Philadelphia, PA

$51.50 - $66.50/hr

Backend technology experience should include Java Enterprise Edition, Enterprise Java Beans 3.0, JPA, and JMS as well as Database experience with Oracle and MySQL. Qualifications * Strong debugging ...

Quantix

Java Engineer

Philadelphia, PA · On-site

$49.50 - $67.75/hr

They are seeking a Java Engineer to join a team responsible for developing applications utilized internationally, focusing on full lifecycle development and backend development. Responsibilities ...

Quantix

Java Engineer

Philadelphia, PA · On-site

$52.25 - $71.75/hr

Java Engineer Location: Philadelphia, PA Type: Direct Hire Client located with offices in ... Responsibilities included full lifecycle development with an emphasis on backend development.

Saransh Inc

Android Developer - Onsite

Wilmington, DE · On-site

$54 - $71/hr

Work with backend engineers to integrate mobile applications with backend services. * Troubleshoot ... Strong proficiency in Kotlin and Java programming languages. * Solid understanding of Android SDK ...

Spruce Infotech Inc

Sr. Java Developer

Wilmington, DE · On-site

$55.50 - $70.75/hr

Provide expert knowledge and guidance for acquisition related backend Java and/or frontend Web features. Ensure that the development teams are adhering to the client SDLC process. Provide technical ...

CYNET SYSTEMS

Angular UI Developer

Malvern, PA · On-site

$60 - $65/hr

Collaborate with UX designers and backend developers to deliver seamless user experiences ... Knowledge of backend development for integration purposes using Java. * Experience with Pandas and ...

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How much do freelance java backend developer jobs pay per hour?

As of Aug 12, 2026, the average hourly pay for freelance java backend developer in Claymont, DE is $53.30, according to ZipRecruiter salary data. Most workers in this role earn between $47.36 and $61.44 per hour, depending on experience, location, and employer.
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Backend API's and Integrations Software Engineer III

RELX

Philadelphia, PA • On-site

Full-time

Re-posted 18 days ago

Job description

Job Summary:
RELX is a mission-driven global organization seeking a Backend API developer. The role involves designing, building, and operating distributed integration services and APIs at scale, with a focus on backend API lifecycle management and enterprise integrations.
Responsibilities:
• Design & Build Distributed Services
• Implementing resilient, observable microservices and integration components (Java preferred; Node.js/JavaScript where appropriate).
• Applying patterns for scaling, fault tolerance, idempotency, and backpressure in distributed environments.
• API Platform & Kong APIM
• Configuring and managing Kong Gateway (routes, services, plugins, rate limiting, auth, mTLS, logging) via declarative config (YAML) and CI/CD.
• Implementing gateway policies for security, traffic control, blue/green/canary releases, and zero-downtime migrations.
• Integrations & Data Facades
• Building and maintaining a FHIR data facade that maps internal domain data to FHIR resources (read/search/transform), ensuring correctness and performance.
• Developing backend integrations with downstream systems (REST, gRPC, messaging/queues) and handle schema/contract evolution.
• API Engineering
• Owning the API lifecycle: design (OpenAPI), implementation, automated testing (unit/integration/contract), versioning, and SLO-driven operations.
• Creating and maintaining OpenAI specs, mocks, and validation pipelines.
• Security & Compliance
• Implementing OAuth2/OIDC flows, token introspection, and service-to-service auth. Apply secure coding practices and least-privilege network policies; partner with InfoSec on reviews.
Qualifications:
Required:
• 3+ years of Professional Experience in backend software engineering.
• Languages: Proficient in Java; working proficiency in JavaScript/Node.js.
• API & Integrations: RESTful API design, OpenAPI/Swagger, contract testing, backward compatibility/versioning.
• API Gateway / Kong APIM: Hands-on experience configuring routes, plugins, auth, rate limiting, and declarative YAML configs; CI/CD integration.
• Distributed Systems: Understanding of microservices fundamentals: statelessness, service discovery, retries/circuit breakers, caching.
• Networking Fundamentals: TCP/IP, DNS, TLS/mTLS, HTTP/2/HTTP/1.1, proxies, load balancing, and common troubleshooting (cURL, traceroute, etc.).
• Data & FHIR Facade: Experience working with HL7 FHIR or adapters; familiarity with FHIR resource modeling and transformations (e.g., Patient, Observation, Encounter).
• Testing & Quality: Unit, integration, and contract testing; test automation and CI/CD pipelines (YAML-based workflows).
• Cloud & Ops: Experience deploying and operating services in a cloud or containerized environment (Docker/Kubernetes).
Company:
RELX is a provider of information-based analytics for professional and business customs. Founded in 1993, the company is headquartered in London, GBR, with a team of 1001-5000 employees. The company is currently Late Stage.

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