Full-Stack Developer — AI-powered internal ops dashboard (Fintech) — API + AI integration

About Saka Saka Tecnologias is a fintech financing smartphones to informal-economy workers — market traders, motorbike-taxi drivers, small vendors — for whom a phone is a work tool, not a consumer item. Customers pay in instalments via mobile money; if they stop paying, the device is progressively restricted until repayment. We are launching a pilot in 2026 and building Saka OS — our internal intelligent operations system — to manage loan approvals, agent recruitment, portfolio monitoring, and weekly learning reports. This is a separate project from our client-facing app (built by another partner). What we need We need an experienced full-stack developer (or a small, named team) to build Saka OS — Phase 1 MVP. This is internal software at the core of how the company runs, so reliability and clean, well-tested code matter more than speed or visual polish. An independent technical reviewer will review architecture and code at each milestone. The system — what is being built Role-based web dashboard (3 roles: Founder, Operations, Field). Each role sees only what is relevant to it. Integration with our loan management system (LMS) via its REST API (OAuth 2.0) — read contracts, payments, activations; write approvals and user creation — plus a device-locking layer for non-payment. Anthropic Claude API as a structured analytics engine (NOT a chat interface) — called programmatically to score loan prospects, assess agent candidates, and generate weekly learning reports. Structured JSON in, structured JSON out. Supabase (or equivalent Postgres) as the database for decisions, audit logs, tasks, and learning insights. 5 automated flows: collection monitoring, loan approval, agent recruitment, PAR30 alerts, weekly learning report. The hardest part of this project is the LMS integration — OAuth 2.0, multiple endpoint groups (read + write), webhooks plus safety polling, and idempotency on payment and device-lock calls. We treat this, not the AI layer, as the core of the work. What we are NOT looking for Agencies that will hand the work to an unnamed rotating team — we want to know exactly who builds this. Developers strong only in mobile/front-end — this is a backend-and-integration project. Anyone who cannot show prior work integrating third-party REST/OAuth APIs and an AI API (Anthropic, OpenAI, or similar) in production. Requirements 5+ years full-stack development; strong backend and API-integration experience. Proven REST API integration with OAuth 2.0 (please cite a concrete example). Experience with an AI API (Anthropic Claude, OpenAI, or similar) in a real product, not just a prototype. Postgres/Supabase; clean data modelling; audit/decision logging. Clear written English. Comfortable with milestone-based delivery on target dates and independent code review. Nice to have PAYG fintech or emerging-market systems; familiarity with an LMS/CRM for emerging markets. RAG / vector-search experience (a later phase adds a "second brain" over company documents). Commercial terms Fixed price per milestone, paid via Upwork escrow per verifiable deliverable — not hourly, not upfront. 100% Saka IP ownership from day one. All code in Saka's own Git repository from the start. Acceptance test before final payment: an independent engineer must clone the repo, follow the docs, and run the system from scratch. If they cannot, the milestone is not met. Technical documentation (API docs, data model, deployment guide) included in scope, not optional. Timeline: ~8–10 weeks starting July 2026. Full technical brief shared with shortlisted candidates under NDA.