Expense Approval Workflow API

Production-style Python/FastAPI backend for employee expense approvals, risk-based routing, decision audit trails, and idempotent workflow operations.

Recruiter Scan

• FastAPI + SQLAlchemy backend with service/repository architecture
• Real workflow state machine: draft, pending manager, pending finance, pending director, approved, rejected, changes requested
• Idempotent expense creation to prevent duplicate submissions
• Risk scoring and approval routing based on claim amount and suspicious text
• Audit trail for every workflow decision
• Request timing middleware, structured JSON logging, Docker, CI, and Pytest coverage

Workflow

flowchart LR
    Draft --> Submitted["pending_manager"]
    Submitted --> Finance["pending_finance"]
    Finance --> Director["pending_director"]
    Submitted --> Approved
    Finance --> Approved
    Director --> Approved
    Submitted --> Rejected
    Finance --> Rejected
    Director --> Rejected

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API Examples

curl -X POST http://localhost:8000/api/v1/expenses \
  -H "Content-Type: application/json" \
  -d '{"employee_id":"E100","department":"Operations","amount":2500,"description":"Client travel","idempotency_key":"claim-001"}'

curl -X POST http://localhost:8000/api/v1/expenses/{claim_id}/decisions \
  -H "Content-Type: application/json" \
  -d '{"actor_id":"M1","actor_role":"manager","action":"approve","comment":"Approved"}'

Local Setup

python3 -m venv .venv
source .venv/bin/activate
make install
make test
make dev

Swagger UI: http://localhost:8000/docs

Why This Project Matters

This project mirrors a real internal enterprise workflow platform: business rules, state transitions, auditability, idempotency, persistence, APIs, and tests. It is designed to be explainable in interviews while still showing backend engineering maturity.