Senior AI-First Full-Stack TypeScript Engineer

Scalable Path is looking for a Senior AI-First Full-Stack TypeScript Engineer with Platform & Workflow Focus to join the team. This is a remote, full-time (40 hours/week) position. Client company description: The client is a well-backed New York startup in building a generic loan origination and automated underwriting platform from scratch. Overview: The client is building a loan origination and automated underwriting platform. The build is AI-primary: most of the code is generated by AI against a loosely specified architecture that needs input/ratification from you. You are the human who owns the platform side of that. You direct the build, review what comes out, finish what the AI cannot, and sign off on merges as one of two engineering reviewers. Your lane is the platform: a Temporal-based process interpreter that runs applications through configured stages, conditions, and exception routing; the guideline package lifecycle (registry, signing, activation, diffs); the CI gates that make acceptance mechanical; and the infrastructure all of that runs on. The co-founder leads the decisioning engine itself — a deterministic evaluator that must replay byte-for-byte and match a reference oracle — and you are its second reviewer, so prior exposure to interpreters, evaluators, or rules engines is a real plus rather than a requirement. This suits someone who has run durable workflows in production and knows where retries, signals, and determinism constraints bite; who can read AI-generated code and tell, quickly, whether it is subtly wrong; and who wants a hand in shaping an architecture rather than inheriting one. If you've worked with Temporal before, that's preferred, but if you've worked with similar workflow tech that's OK, too. Responsibilities: - Own the Temporal workflow layer: a generic process interpreter driven by per-product configuration, the condition subsystem, and exception routing into a minimal review workbench. - Design the boundary with the system of record (owned by the database-focused engineer) so workflow retry semantics and outbox delivery compose rather than collide. - Own guideline package lifecycle: the package registry, signing, activation records, and diffs between versions. - Own the CI gates and the performance and replay rigs: the harness that re-decides historical applications and proves the output has not drifted. - Review infrastructure changes — CDK in TypeScript, CI/CD, and the custom CI gates — alongside the security engineer who owns the control surface. - Second-review the decisioning engine alongside the co-founder, who leads it: deterministic semantics, trace emission, the numerics discipline (a decimal type enforced by lint bans), and cross-checks against the reference oracle over the golden-vector corpus. Qualifications: - Senior full-stack TypeScript with a platform center of gravity. You direct AI tooling to do most of the typing, and you could code all of it yourself if you had to — the second part is what makes the first part safe. - Expert TypeScript. You will review type-level machinery and lint-enforced invariants, not just application code. - Production experience with Temporal or another durable-execution engine (Cadence, Restate, Step Functions): activity retries, determinism constraints on workflow code, signals, and time-skipping test harnesses. This is the core of the seat. - Production AWS, and comfortable reviewing CDK-in-TypeScript and CI/CD changes. - You are comfortable being the reviewer of record. You can read a workflow, a migration, or an evaluator produced by someone — or something — else and tell whether it is right, and you would rather own that judgment than the keystrokes. - A plus: exposure to interpreters, expression evaluators, rules engines, or decision-table languages (FEEL/DMN). The co-founder leads the decisioning engine; you will be its second pair of eyes. - A plus: property-based testing (fast-check or equivalent), and the ability to read JVM code — the reference oracle is a Java implementation you will cross-check against, not write. - Nice to have: lending or fintech background and React for the review workbench. - A plus: experience in mortgage or consumer lending — origination, underwriting, servicing, or the vendor ecosystem around them (credit bureaus, AVMs, fraud, e-signature, etc.). Relationships - who you'll be working with: You will work directly with the co-founder — technical, hands-on, and the product owner — alongside a second senior full-stack engineer with a database focus, a part-time security engineer, a junior engineer who joins a month or two in, and a business-side integrations lead who owns vendor relationships. The originating lender's own underwriters validate and countersign what the platform decides. No layers between you and the decision-maker. You are expected to overlap with the US East Coast working day for at least four hours. Expected contract duration: 12+ months If all works out this is expected to be an ongoing role Preferred regions: The client's preference is for candidates to be located in Latin America or Canada. Required skills: English (Must have)TypeScript (Must have)Node.js (Must have)AWS (Must have)Temporal (Strongly preferred)React (Nice to have)