Architecture

Tech stack by layer

Layer	Technology	Role
Frontend	Next.js (App Router)	Web2 UI — no crypto terminology
Backend / API	NestJS	Orchestrates the complete flow
Database	Supabase (PostgreSQL) + RLS	Payment metadata, users, projects
Invisible wallets	Privy (embedded wallets)	Wallet per coordinator — email login
Disbursements	Stellar Disbursement Platform (SDP)	USDC disbursements to area wallets
Key custody	AWS KMS	Encrypted private keys — never in plain text
Blockchain	Stellar	Immutable transaction record
Indexer	Horizon API (polling every 30s)	Syncs on-chain data with Supabase
Fiat off-ramp	Bitso (CO/CR) · Belo / Lemon Cash (AR)	USDC to local currency
File storage	Supabase Storage	Attachments (invoices, photos) — off-chain
Frontend deploy	Vercel
API / workers deploy	Railway
Cloud DB	Neon (Postgres) + Upstash (Redis)

System layers

+------------------------------------------+
|           FRONTEND (Next.js)             |  <- User sees: accounts, payments, reports
+------------------------------------------+
|            API (NestJS)                  |  <- Orchestrates: SDP, Privy, off-ramp, KMS
+------------+----------+------------------+
|  Supabase  |  AWS KMS |  Horizon Indexer |  <- Data + Keys + On-chain sync
| (off-chain |  (private|  (every 30 sec)  |
|  metadata) |   keys)  |                  |
+------------+----------+------------------+
|         STELLAR NETWORK                  |  <- Immutable txHash record
|   SDP · Privy Wallets · Soroban          |
+------------------------------------------+
|         OFF-RAMP (Bitso / Belo)          |  <- USDC -> COP / CRC / ARS
+------------------------------------------+

Multi-tenant data isolation

Row Level Security (RLS) in Supabase — every query is automatically filtered by foundation
Independent Stellar wallets per foundation
Middleware validates the user token before any query
A user from one foundation cannot access data from another under any circumstance