Senior Backend Software Engineer, TS/SCI with CI Poly - $180K-$210K + 15% 401k

About Millennial Software:

Millennial Software is revolutionizing the landscape of security and defense by leveraging our core competencies in software development, automation, DevSecOps, and machine learning.

• We are an employee-owned company, every employee receives equity in the company 
• 100% company-paid medical, dental, and vision premiums for you and all dependents
• Ability to get increased salary if you don't need medical/dental/vision
• 100% company-paid disability and life insurance benefits 
• 15% 401(k) company contribution 
• 30 days of PTO/holidays 
• Generous training budget
• Paid Paternal and Maternal Leave
• Business development / growth incentives 
• Top notch company swag

Job Description: 

Millennial Software is seeking a Senior Backend Software Developer to join our collaborative team supporting National Security. You’ll design, develop, and support scalable APIs and services using a tech stack that power data-driven applications and enable mission-critical decisions. You will focus on backend architecture, data modeling, integrations, performance, and reliability while partnering with frontend engineers, analysts, and users. 

The ideal candidate is passionate about the full lifecycle—design, coding, testing, deployment, and sustainment—and comfortable delivering secure, high-quality tools in mission environments.

Essential Functions: 

• Design, implement, and maintain backend services, APIs, and integrations that support product features. 
• Develop data models and persistence layers; ensure data quality, integrity, and performance. 
• Build reliable service-to-service communication and integration patterns (REST/GraphQL, messaging, streaming). 
• Apply secure coding practices and ensure appropriate authentication/authorization patterns. 
• Create and maintain automated tests (unit/integration) and participate in peer code reviews. 
• Diagnose and resolve production issues; improve reliability through monitoring, alerting, and runbooks. 
• Collaborate with frontend engineers and other stakeholders to define contracts and support end-to-end delivery. 
• Identify bottlenecks and drive performance improvements (latency, throughput, resource utilization). 
• Produce technical documentation for systems, APIs, and operational procedures.

Required Qualifications: 

• Demonstrated experience building and operating production backend services and APIs. 
• Proficiency in at least one backend language (e.g., Python, Java, Go, C#, Node.js) and common frameworks. 
• Strong understanding of API design, authentication/authorization concepts, and service reliability. 
• Experience with relational and/or NoSQL databases, query optimization, and schema/data modeling. 
• Experience with messaging and queuing platforms such as Kafka, RabbitMQ, or similar. 
• Familiarity with testing strategies and CI workflows; comfort with debugging and incident triage. 
• Ability to collaborate cross-functionally and communicate technical decisions clearly. 
• Experience creating and maintaining Docker containers, Helm charts, orchestration platforms such as Kubernetes clusters, and using cloud infrastructure services (AWS/Azure/GCP). 
• Bachelor’s degree in a related field or equivalent practical experience.
• At least 10+ years performing backend software engineering.  
• Active TS/SCI clearance. 
• Ability to work on-site at one of the following locations - Virginia: Fairfax, Chantilly, McLean, Sterling or Colorado: Colorado Springs.

Nice to have: 

• Experience designing distributed systems (caching, queues, streaming, idempotency, retries, circuit breakers). 
• Observability experience: metrics, logging, tracing; familiarity with SLOs/SLIs and incident response practices. 
• Experience with data pipelines, ETL/ELT, or search platforms. 
• Knowledge of security best practices (threat modeling, secrets management, secure SDLC). 
• Experience with performance testing and capacity planning. 

Millennial Software Solutions Inc. is an Equal Opportunity Employer and does not discriminate in employment on the basis of race, color, religion, sex, national origin, political affiliation, sexual orientation, gender identity, marital status, disability and genetic information, age, membership in an employee organization, or other non-merit factor.