Demo

API Senior Software Engineer

Apex Systems
Milwaukee, WI Contractor
POSTED ON 4/22/2026
AVAILABLE BEFORE 5/21/2026
Job#: 3031195

Job Description:

Our great client in Downtown Milwaukee has an immediate opening for a API Software Engineer. If you are interested please apply with resume to [email protected] .

Collaborate with the API Enablement team to build and maintain enterprise-grade internal tooling, API governance automation, and developer experience platforms. Contributes to the design and delivery of cross-cutting technical solutions — including API quality enforcement engines, SDK generators, and the enterprise API catalog — that enable domain teams to build and publish high-quality APIs at speed. Supports contract-first API development practices and tooling built around OpenAPI Specification (OAS). Participates in refinement, solution definition, and decomposition of features into deliverable work items. Works across organizational boundaries with domain engineering teams, Enterprise Architecture, and API Management to deliver on the team's highest-priority initiatives. Finds opportunities for continuous improvement and owns initiatives that help the team get better. Engages collaboratively, respects diverse perspectives, and communicates effectively with both technical and non-technical audiences.

Qualifications

  • Bachelor's Degree or equivalent experience
  • 8 years of professional software development experience required
  • 5 years of experience with API design, development, and governance including OpenAPI Specification (OAS) and REST best practices
  • Experience with Java and/or Node.js/TypeScript
  • Proficient in practices such as contract-first API design, API quality automation, and internal platform/tooling development
  • Proven track record of architecting and delivering significant developer tooling or platform solutions (e.g., SDK generators, compliance engines, API catalogs)
  • Capable of working autonomously and delivering with minimal direction in an enterprise environment
  • Effective communicator with product, engineering, architecture, and business partners, with proven ability to communicate to both technical and non-technical audiences in varying forms and levels of detail

Skills for Sourcing

Must-Have Skills:

API Development (REST / OpenAPI), Java or Node.js/TypeScript, Internal Developer Tooling / Platform Engineering, Contract-First API Design

Nice-to-Have Skills:

API Quality / Compliance Automation (e.g., Spectral), Client SDK Generation (e.g., OpenAPI Generator / Kiota), API Catalog / Developer Portal Experience, Enterprise Authorization Patterns (PBAC or similar)

EEO Employer

Apex Systems is an equal opportunity employer. We do not discriminate or allow discrimination on the basis of race, color, religion, creed, sex (including pregnancy, childbirth, breastfeeding, or related medical conditions), age, sexual orientation, gender identity, national origin, ancestry, citizenship, genetic information, registered domestic partner status, marital status, disability, status as a crime victim, protected veteran status, political affiliation, union membership, or any other characteristic protected by law. Apex will consider qualified applicants with criminal histories in a manner consistent with the requirements of applicable law. If you have visited our website in search of information on employment opportunities or to apply for a position, and you require an accommodation in using our website for a search or application, please contact our Employee Services Department at [email protected] or 844-463-6178.

Apex Systems is a world-class IT services company that serves thousands of clients across the globe. When you join Apex, you become part of a team that values innovation, collaboration, and continuous learning. We offer quality career resources, training, certifications, development opportunities, and a comprehensive benefits package. Our commitment to excellence is reflected in many awards, including ClearlyRated's Best of Staffing® in Talent Satisfaction in the United States and Great Place to Work® in the United Kingdom and Mexico. Apex uses a virtual recruiter as part of the application process. Click here for more details.

Apex Benefits Overview: Apex offers a range of supplemental benefits, including medical, dental, vision, life, disability, and other insurance plans that offer an optional layer of financial protection. We offer an ESPP (employee stock purchase program) and a 401K program which allows you to contribute typically within 30 days of starting, with a company match after 12 months of tenure. Apex also offers a HSA (Health Savings Account on the HDHP plan), a SupportLinc Employee Assistance Program (EAP) with up to 8 free counseling sessions, a corporate discount savings program and other discounts. In terms of professional development, Apex hosts an on-demand training program, provides access to certification prep and a library of technical and leadership courses/books/seminars once you have 6 months of tenure, and certification discounts and other perks to associations that include CompTIA and IIBA. Apex has a dedicated customer service team for our Consultants that can address questions around benefits and other resources, as well as a certified Career Coach. You can access a full list of our benefits, programs, support teams and resources within our ‘Welcome Packet’ as well, which an Apex team member can provide.

Apex Systems is a world-class IT services company that serves thousands of clients across the globe. When you join Apex, you become part of a team that values innovation, collaboration, and continuous learning. We offer quality career resources, training, certifications, development opportunities, and a comprehensive benefits package. Our commitment to excellence is reflected in many awards, including ClearlyRated's Best of Staffing® in Talent Satisfaction in the United States and Great Place to Work® in the United Kingdom and Mexico. Apex uses a virtual recruiter as part of the application process. Click here for more details.

Apex Benefits Overview: Apex offers a range of supplemental benefits, including medical, dental, vision, life, disability, and other insurance plans that offer an optional layer of financial protection. We offer an ESPP (employee stock purchase program) and a 401K program which allows you to contribute typically within 30 days of starting, with a company match after 12 months of tenure. Apex also offers a HSA (Health Savings Account on the HDHP plan), a SupportLinc Employee Assistance Program (EAP) with up to 8 free counseling sessions, a corporate discount savings program and other discounts. In terms of professional development, Apex hosts an on-demand training program, provides access to certification prep and a library of technical and leadership courses/books/seminars once you have 6 months of tenure, and certification discounts and other perks to associations that include CompTIA and IIBA. Apex has a dedicated customer service team for our Consultants that can address questions around benefits and other resources, as well as a certified Career Coach. You can access a full list of our benefits, programs, support teams and resources within our ‘Welcome Packet’ as well, which an Apex team member can provide.

Apex Systems is part of the Commercial Segment of ASGN Incorporated.

NYSE: ASGN

4400 Cox Road

Suite 200

Glen Allen, Virginia 23060

Apex Systems is an equal opportunity employer. We do not discriminate or allow discrimination on the basis of race, color, religion, creed, sex (including pregnancy, childbirth, breastfeeding, or related medical conditions), age, sexual orientation, gender identity, national origin, ancestry, citizenship, genetic information, registered domestic partner status, marital status, disability, status as a crime victim, protected veteran status, political affiliation, union membership, or any other characteristic protected by law. Apex will consider qualified applicants with criminal histories in a manner consistent with the requirements of applicable law. If you have visited our website in search of information on employment opportunities or to apply for a position, and you require an accommodation in using our website for a search or application, please contact our Benefits Department at [email protected] or 804-523-8228. (Do not submit resumes or solicit consultants to this email address). UnitedHealthcare creates and publishes the Transparency in Coverage Machine-Readable Files on behalf of Apex Systems.

Salary : $55 - $60

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