Full-Stack Engineer — Amazon Ads API (NestJS + Next.js) to finish a Sponsored Products dayparting tool

We have a substantially built Amazon Sponsored Products dayparting tool and need an experienced engineer to complete it. The analysis side is done: OAuth account linking, hourly performance ingestion (CSV report + Amazon Marketing Stream), and an interactive CPC/ACOS heatmap that lets us design hourly bid-modifier schedules. The main missing piece is the execution layer — pushing bid adjustments back to Amazon — plus hardening auth and a few correctness fixes. The data model and scheduler scaffolding for this already exist; we need someone who can build on an existing, well-structured codebase rather than start from scratch.

Required skills
NestJS (v11) and TypeScript — strong. You'll be extending existing modules, DTOs, guards, and services, not greenfield.
Amazon Advertising API — demonstrable, hands-on. Specifically the Sponsored Products endpoints for campaigns, ad groups, bidding, and bid adjustments/dayparting, plus how bid rules are actually applied. This is the single most important skill — please describe a real Amazon Ads integration you've shipped.

Amazon LWA OAuth and token/refresh lifecycle.
Prisma (v7) with PostgreSQL, including migrations and raw SQL.
Next.js (v16, App Router) and React (v19) — React Query, Zod, Jotai a plus.
Auth implementation: JWT / session-based auth wired end-to-end (frontend ? backend).
Comfortable with an existing test suite (Jest), Docker, and reading someone else's code carefully.

Nice to have
AWS SNS/SQS (the Marketing Stream ingestion uses them) and S3.
OpenTelemetry / Sentry.
Experience with Amazon Ads API rate limits and throttling at scale.

Renumeration will be discussed with shortlisted candidates. Estimate provided.
In your application, please:

1. Link an Amazon Advertising API integration you've built and say which endpoints you used.
2. Tell us, in your own words, how Amazon Sponsored Products handles hourly bid adjustments/dayparting today, and any constraints or gotchas.
3. Confirm you're comfortable extending an existing NestJS + Next.js codebase (~90 backend files, Prisma schema, existing tests).