Senior Software Engineer | 100% Remote

Company Description
NeoEvolution AI helps organizations challenge the status quo by applying exponential technologies to real-world business problems. The company focuses on building collective intelligence with AI to drive transformation across social, political, and economic spheres. NeoEvolution AI partners with clients to design and implement innovative AI solutions that enhance decision-making, efficiency, and resilience. Team members collaborate in a forward-looking environment that values curiosity, ethical use of technology, and measurable impact for businesses and communities.
Location: Remote (US)
Experience: 5+ years
Candidate Location: Costa Rica (this is a MUST)
Contract Term
This is a 100% fully remote independent contract opportunity to work for a large US-based client.
Candidates must be located in Costa Rica.
Long-term contract with no specified termination period.
Working hours must overlap with United States business hours
About the Role
A Senior Software Engineer helps own the source of truth for care-provider organizations, locations, users, and permissions. The team builds the business-to-business (B2B) side of a loyalty platform used by tens of thousands of aesthetics practices. It isn't payments or loyalty itself, but those depend on it: checkout and payments, pricing and loyalty programs, feature enablement, and partner integrations all rely on this platform to know who a practice is, what it can access, and who can act for it.
This is a hands-on position for someone who writes production code every day, reviews a large share of the team's pull requests, and is the go-to person for APIs, SDKs, data integrity, and authentication questions.
What You'll Do
Own the user, role, and organization domains, and build and evolve the APIs and SDK contracts that other teams consume.
Move logic from older serverless and GraphQL services into NestJS domain services without breaking anyone who depends on them.
Protect data integrity through lifecycle automation driven by SAP data (archival, transfers), backfills, reconciliations, and large account migrations.
Review code as a core part of the job: this role has been reviewing roughly 35–65% of the team's pull requests.
Lead cross-team design work on consumer SDKs, user APIs, data integrity, and authentication, and write RFCs and migration plans.
Keep the platform healthy through runtime upgrades, CI hardening, test infrastructure, and performance tuning.
What We're Looking For
5+ years of software-engineering experience, with substantial backend work.
TypeScript and Node.js at production depth, including NestJS for domain services.
In-depth PostgreSQL: schema design, migrations, indexing, and reading query plans (EXPLAIN ANALYZE), using TypeORM.
AWS serverless and event-driven design: Lambda, SQS (including FIFO queues and dead-letter queues), SNS, and Parameter Store.
API design: REST with OpenAPI and generated, typed SDKs for consumers, plus GraphQL for older services.
Authentication and authorization: role-based access, Okta, service-to-service authentication through a central IAM, and token-based partner access (DPoP).
Strong testing discipline: Jest, with integration tests backed by Testcontainers.
Care with data: treats a migration or backfill as a production change, with a written plan, dry runs, reconciliation, and a rollback path.
Experience replacing a legacy system step by step, using feature flags, fallbacks, or parallel runs, and able to explain the trade-offs.
Consumer empathy: thinks about API stability, versioning, and how changes affect downstream teams.
Raises the level of the team through thorough code reviews and mentoring, not only through their own output.
Follow-through: gets work merged, or deliberately closes it, rather than leaving it unfinished.
Clear written and spoken English, including RFCs and migration plans that other teams can act on.
Nice to Have
Temporal or another durable-workflow engine.
Terraform.
Enough Kubernetes to deploy and debug: Kustomize overlays and IAM roles for service accounts (IRSA).
Datadog for observability.
GitHub Actions and ArgoCD for CI/CD.
If you enjoy owning the core data and APIs that other teams depend on, and you take pride in careful migrations and clean contracts, we'd love to hear from you.

Work arrangement
Yes