Senior Software Engineer | Product Foundations

castaigroupinc; United States; Remote; USD 80,000 - 111,000; Full time

Benefits offered by this job

Remote-first (EU eligibility)

Equity options

Equipment budget

Learning budget

Team-building budget

Extra days off

Personal project time (10%)

Annual hackathon

Fast-paced project cycles

Travel covered onboarding

Job summary

castaigroupinc is seeking a remote-first senior engineer to own end-to-end back-end services in Go, focusing on trust, authentication, billing, and telemetry within a cloud-native platform. You will work across domains, drive design decisions, and participate in on-call rotations as needed.

The role emphasizes system correctness, scalability, and security, with a strong emphasis on collaboration and proactive problem-solving in a fast-paced startup environment.

Qualifications

• Strong fundamentals in software engineering with clean abstractions.
• Production Go experience or similar systems programming language.
• Background building trust-critical systems at scale (auth, billing, or data).
• Solid API design with versioning, auth, idempotency, and async patterns.
• Hands-on Kubernetes experience with deployment or debugging on a cluster.
• Debugging and performance tuning across large data stores.
• Experience with AI coding agents and agentic development workflows.
• Excellent written and spoken English; startup mindset and adaptability.
• Willingness to participate in on-call rotation.

Responsibilities

• Design, build, and operate backend services in Go used by customers.
• Own features end-to-end from design to production rollout.
• Debug complex production issues in security-, billing-, or trust-critical flows.
• Collaborate with product and other engineering teams to solve non-textbook problems.
• Contribute to product direction and backlog planning.

Skills

Go

Kubernetes

API design

Performance tuning

Distributed systems

On-call readiness

English communication

Tools

Prometheus

Grafana

OpenTelemetry

PostgreSQL

Job description

Role overview

A remote-first senior engineering role sits on the team responsible for the trust and accounting layer of a cloud-native automation platform that runs inside Kubernetes environments. The work spans several interconnected domains: authentication and authorization, billing, audit trails, notifications, feature flags, real-time cloud pricing intelligence, and reporting that turns high-volume time-series data into accurate savings insights. The senior engineer will own services end-to-end where correctness directly affects customer trust, money, and security.

Responsibilities

• Design, build, and operate backend services in Go that other teams and customers rely on for correctness.
• Own features end-to-end, from design and implementation through testing and production rollout.
• Debug complex production issues involving security-, billing-, or trust-critical flows.
• Collaborate with product and other engineering teams to solve problems that do not have textbook solutions.
• Contribute to product direction and backlog, helping shape what gets built next as well as how it is built.

Requirements

• Strong software engineering fundamentals: the ability to design clean abstractions, write maintainable code, and justify architecture choices.
• Production experience with Go, or comparable systems-programming expertise in a similar language.
• Background building or operating trust-critical systems at scale, such as authentication and authorization, billing, or financial-adjacent data.
• Solid grasp of API design best practices: versioning, backward compatibility, auth, idempotency, and async patterns.
• Hands-on Kubernetes experience, including deploying or debugging workloads on a cluster.
• Debugging, optimization, and performance-tuning skills, including query profiling, index design, and database tuning beyond ORM usage.
• Track record operating systems under high load and identifying bottlenecks rather than simply scaling out.
• Experience with AI coding agents and agentic development workflows.
• Strong verbal and written English skills, plus a startup mindset that is adaptable, proactive, and comfortable in ambiguity.
• Willingness to participate in an on-call rotation where required.

Nice to have

• Multi-tenant identity system design, including SSO.
• Enterprise identity protocols such as SAML, OIDC, and SCIM.
• Production experience with billing, audit-trail, notification, or feature-flag systems.
• Familiarity with cloud provider pricing or billing APIs across major hyperscalers, or tracking Spot instance availability.
• High-cardinality time-series ingestion and querying at scale.
• Understanding of Kubernetes internals, CI/CD and DevOps practices, and observability tooling such as Prometheus, Grafana, or OpenTelemetry in production.

Benefits and work setup

• Remote-first environment, with eligibility restricted to candidates residing in specific European countries.
• Gross monthly salary range of €6,500–€9,000 depending on experience, plus separate compensation for passive on-call coverage and active interventions.
• Equity options, equipment budget, learning budget, team-building budget, and extra days off for work-life balance.
• Around 10% of work time allocated to personal projects or self-improvement, an annual hackathon, and a fast-paced workflow where most feature projects complete in one to four weeks.
• Onboarding involves travel to a specific city, with travel costs covered by the employer.