Staff Software Engineer

Socket.dev; Hinoba-an; On-site; PHP 1,800,000 - 2,800,000; Full time

Job summary

FirstWork is hiring a Staff Backend Engineer to architect scalable AI-powered HR operations platforms. You will own core domains such as the agent runtime, rules engine, and data models, while pushing LLM-driven features deeper into the product and ensuring deterministic, auditable outcomes.

You will design safety, evaluation, and data-architecture components to support enterprise-scale AI decisions across global workflows, with a focus on performance and reliability.

Qualifications

• 8+ years of professional backend engineering experience.
• Experience scaling a first architecture to enterprise scale.
• Deep relational database expertise with production saturation diagnosis.
• Production experience with LLM or vision-model systems and cost control.
• Experience with multi-tenant, configurable products.
• Measurement-first approach: profiling and traces before opinions.
• Influence through clear writing and demonstrated results.

Responsibilities

• Take end-to-end ownership of core domain: the agent runtime, the compliance and rules engine, the worker data model, or integrations.
• Push LLMs and agentic AI deeper into the product, and draw the line between inference and deterministic rules.
• Design the safety properties of agents that act in external systems, including idempotency, retries, isolation, and human escalation.
• Build the evaluation and accuracy infrastructure that makes AI decisions defensible in a regulated context.
• Keep inference viable at scale through model routing, caching, and batching, with cost per transaction as a tracked metric.
• Design data models with long‑lived constraints, including audit logs, compliance clocks, and credential lifecycles.
• Drive the data architecture roadmap: read replicas, logical sharding, CDC‑fed projections, and a search tier.
• Enforce multi‑tenancy, permissions, and audit trails as invariants guaranteed by design and by test.
• Act as a technical lead through design review, incident command, and mentoring senior engineers.
• Work directly with product and customers to turn bespoke requests into platform capabilities.

Skills

Backend engineering

Relational databases

Distributed systems

LLMs / AI models

Multi-tenant architecture

Performance optimization

Tools

PostgreSQL

Distributed systems tooling

Job description

FirstWork is building the next generation of agentic AI products for frontline hiring, the work that gets roughly 80% of the world's workforce hired, verified, and paid. We're looking for a Staff Backend Engineer to architect the systems that let those agents run at the next order of magnitude, and to build the new product lines we are launching with AI designed-in from the start.

In this role, you'll set the technical direction for a core domain and work closely with product, design, and engineering leadership to get intelligent systems into a shape customers can configure and rely on. This is a hands‑on architecture role: you'll still write code, and you'll see your decisions tested against live enterprise volume. The challenges ahead are scaling throughput, latency, and data volume as usage compounds, and keeping AI agents accurate, reliable, and economical as that happens.

The scale we run at

• ~50,000 workers a week move through our hiring and onboarding flows.
• 2.5 million API requests a day across the platform.
• Millions of document pages a year processed by AI agents, across 40+ countries and a dozen-plus languages.
• Global staffing, logistics, healthcare, marketplace, and employment platforms across the US, UK, EU, LATAM, and India.
• Billing on work performed, per document validated and per agent action executed, which makes product design, cost per unit, and gross margin one conversation.

What you'll do

• Take end-to-end ownership of core domain: the agent runtime, the compliance and rules engine, the worker data model, or integrations.
• Push LLMs and agentic AI deeper into the product, and draw the line between what belongs in inference and what belongs in deterministic, auditable rules.
• Design the safety properties of agents that act in external systems, including idempotency, retries, isolation, and human escalation.
• Build the evaluation and accuracy infrastructure that makes AI decisions defensible in a regulated context.
• Keep inference viable at scale through model routing, caching, and batching, with cost per transaction as a tracked metric.
• Design data models with long‑lived constraints, including audit logs, compliance clocks, and credential lifecycles.
• Drive the data architecture roadmap: read replicas, logical sharding, CDC‑fed projections, and a search tier.
• Enforce multi‑tenancy, permissions, and audit trails as invariants guaranteed by design and by test.
• Act as a technical lead through design review, incident command, and mentoring senior engineers.
• Work directly with product and customers to turn bespoke requests into platform capabilities.

What we need

• 8+ years of professional backend engineering experience.
• Experience at a company that outgrew its first architecture, and a hand in scaling it incrementally.
• Deep relational database expertise, including diagnosing saturation in production.
• Production experience with LLM or vision‑model systems: evaluation, accuracy, cost control, and fallback design.
• Strong distributed systems judgement across idempotency, retries, queue lag, and partial failure.
• Experience with multi‑tenant, configurable products.
• A measurement‑first approach: profiles and traces before opinions.
• Influence through clear writing and demonstrated results.

Nice to have

• Built agentic systems where an agent takes real action in an external system.
• Temporal or another durable execution engine at production scale.
• Event‑driven architecture and CDC pipelines feeding read stores.
• Rules engines, policy‑as‑code, or workflow orchestration.
• Compliance, identity, payroll, or financial infrastructure background.
• Experience platformizing a single‑vertical product for additional verticals.
• Experience in an AI‑first, fast‑moving product environment.
• Familiarity with AI‑assisted development tools such as Claude.

About FirstWork

FirstWork is an applied AI company building the HR operations platform behind frontline hiring, the largest, least automated, and most heavily regulated labour market in the world. One system carries a worker from application through onboarding, compliance verification, training, and payroll, for hundreds of enterprise customers.

We are AI‑native. Our document agents read and validate credentials against policy. Our browsing agents drive government portals through the browser, where the only interface is the UI. Our voice and conversational agents screen and follow up with candidates. Our rule engines adjudicate compliance decisions and produce the audit trail behind them. Our agents are doing regulated work in production today.

Firstwork is an equal opportunity employer. We evaluate applicants without regard to race, color, religion, sex, national origin, age, disability, or any other protected status.