Indian Lending Platform (Beta) — nano-service event-driven architecture with Ed25519 cryptographic attestation.

A nano-service platform for Indian retail lending. Designed for RBI Digital Lending Guidelines compliance, with DPDPA 2023 data protection and 30+ independently deployable services connected by an event bus with Ed25519 cryptographic attestation.

Beta — not yet production-ready. Known gaps include stubbed PAN / Aadhaar / CKYC / CIBIL integrations, no video KYC, stubbed e-NACH / UPI Autopay mandate collection, basic RBAC only, undocumented disaster-recovery procedures, and rough developer experience (no prebuilt Docker images, no Helm charts, manual service wiring required). See Status below.

• 31 nano-services — KYC / AML (PAN + Aadhaar Verhoeff), CIBIL / Experian / Equifax credit bureau, CKYC registry, RBI rate-capped pricing, KFS generation, DPDPA consent + DSR, Razorpay PG, risk scoring, fraud detection, collections, recovery, notifications, governance
• Event-driven — Typed events with Ed25519 signatures, saga orchestration, dead-letter queues, circuit breakers
• Pluggable backends — Memory / filesystem / Postgres stores; local / SQS / Modal event bus; console / OTLP tracing
• 1167 tests — Rate limiting, idempotency guards, PII redaction, Prometheus metrics
• DPDPA 2023 + RBI DLG aligned — Per-product rate caps, all-in-cost APR, penal-interest cap, KFS cooling-off, consent lifecycle, DSR fulfillment, breach notification, auto-purge

This is the v0.9 release line. Security and correctness fixes from the hardening pass:

• Ed25519 event signatures bind the source and enforce a 5-minute replay window; private keys persist through the configured SecretsManager.
• /v1/publish binds the publisher identity from the request payload, with an optional authz gate.
• PII is redacted at the audit, DLQ, and Prometheus tag boundaries with token-based field matching.
• DLQ, bus buffer, and idempotency guard are bounded against unbounded memory growth.
• Config redaction covers every secret-shaped field; config data_dir is validated against sensitive system paths.
• Indian holiday calendar covers 2025–2030 with a sensible fallback for unknown years.
• KFS APR math, pricing EMI, NPA thresholds, and the underwriter rule engine are all aligned with RBI norms.
• Real KYC provider integrations — PAN (NSDL/ITD), Aadhaar (UIDAI KUA), CIBIL, and CKYC have full wire-protocol clients in services/kyc_providers/. They are wired into the compliance and credit-bureau services and configured via Configuration.kyc_providers.
• Production Docker image — multi-stage build, non-root user, healthcheck, OCI labels, Buildx + GitHub Actions workflow. Build with ./scripts/build-image.sh or docker build -t underwrite:dev ..
• CI matrix 3.10-3.13, coverage gate 80%, ruff format check, TruffleHog secret scan, mypy / bandit / pip-audit.

Remaining work to reach v1.0:

• Video KYC provider integration (Digilocker, NSDL).
• Helm chart for k8s deployment.
• Pre-built multi-arch (amd64 + arm64) images.
• Read-only underwrite role for psql / Vault operations.
• Production runbook for on-call (incident response, key rotation, DLQ replay).

pip install underwrite
pip install "underwrite[risk,serve,postgres,otlp,vault,aws]"

git clone https://github.com/sachncs/underwrite.git
cd underwrite
./setup.sh
source .venv/bin/activate
pip install -e ".[dev,risk,serve,postgres,otlp,vault,aws]"

• Python 3.10+
• PostgreSQL 14+ (optional — memory / filesystem backends work without it)
• Docker (optional — for docker compose up with Postgres + Vault + OTLP)

git clone https://github.com/sachncs/underwrite.git
cd underwrite
./setup.sh
source .venv/bin/activate
python -m pytest tests/ --tb=short -q   # 1167 tests

To run an Indian lending scenario:

underwrite init
# edit underwrite.json to enable: mechanism,audit,risk,fraud,compliance,consent,credit_bureau,kfs,pricing,underwriter,decision
underwrite run mechanism audit risk fraud compliance consent credit_bureau kfs pricing underwriter decision
# In another terminal:
python docs/examples/indian_lending.py
# See docs/QUICKSTART.md for the full walkthrough

underwrite

Commands:
  init [PATH]              Create default config
  run <service>...         Start one or more services
  list                     List all 31 nano-services
  identity <service>       Generate Ed25519 keypair
  health                   System health status
  dlq [--replay] [--max N] Show or replay dead-letter queue
  metrics                  Metrics snapshot (Prometheus-format on /v1/metrics)
  migrate                  Run pending schema migrations
  serve                    Start HTTP daemon (requires [serve] extra)

Authentication via Authorization: Bearer <token> when started with --require-auth.

Configure via JSON file (created with underwrite init), env vars, or both (env vars override). See .env.example for every supported variable — including RBI pricing caps, AML thresholds, credit-bureau API keys, Razorpay credentials, and DPDPA retention periods.

Each nano-service extends NanoService with a single handle(event: Event) -> None:

1. Subscribe — declare interest in event types via config
2. Dispatch — handler wrapped with authz, idempotency, tracing, metrics, timeout
3. Emit — self.emit(event) signs with Ed25519 and publishes to the bus
4. Persist — state via Store (MemoryStore / FileStore / PostgresStore)

Cross-cutting concerns (authz, tracing, metrics, sagas, supervisor, circuit breaker) are injected by the bus and runtime — not inherited by services.

underwrite/
├── underwrite/                    # Source (90+ modules, fully typed)
│   ├── __config__.py              # Pydantic configuration (28 sections)
│   ├── __bus__.py                 # Event bus — pub/sub, DLQ, rate limiter
│   ├── __store__.py               # State store — memory / file / postgres
│   ├── __saga__.py                # Saga orchestrator
│   ├── __authz__.py               # Access control & Ed25519 verification
│   ├── __identity__.py            # Ed25519 key management
│   ├── __events__.py              # 105+ event types
│   ├── __pii__.py                 # PII redaction (Aadhaar, PAN, etc.)
│   └── services/                  # 31 nano-services
│       ├── base.py                # NanoService ABC
│       ├── mechanism/             # Delegation state machine (core)
│       ├── compliance/            # KYC/AML — PAN category, Aadhaar Verhoeff, risk score
│       ├── pricing/               # RBI caps, APR, EMI, penal interest, foreclosure
│       ├── kfs/                   # Key Fact Statement generation
│       ├── consent/               # DPDPA consent lifecycle
│       ├── dsr/                   # Data Subject Rights fulfillment
│       ├── credit_bureau/         # CIBIL/Experian/Equifax + CKYC
│       ├── razorpay/              # Payment gateway integration
│       ├── risk/                  # ML risk scoring
│       ├── fraud/                 # Fraud detection
│       ├── audit/                 # Event ledger (PII-redacted)
│       ├── npa/                   # Asset classification (SMA/NPA/DLG)
│       ├── recovery/              # Default recovery (store-backed)
│       └── ...                    # 17 more services
├── tests/                         # 58 test files, 1167 tests
└── docs/                          # 9 updated docs for Indian market

pip install -e ".[dev,risk,serve,postgres,otlp,vault,aws]"
pytest tests/ --tb=short -q
ruff check underwrite/
ruff format underwrite/
mypy underwrite/
bandit -r underwrite/
pip-audit
mutmut run                     # mutation testing (optional)

pytest tests/ --tb=short -q
pytest tests/ -x --timeout=30
pytest --cov=underwrite --cov-report=term-missing

The suite contains 1167 tests across rate limiting, idempotency, PII redaction, RBAC, saga orchestration, and Prometheus metrics.

pip install build
python -m build

pytest && ruff check underwrite/ && mypy underwrite/ && bandit -r underwrite/
# Bump version (setuptools_scm derives the version from git tags)
git tag vX.Y.Z && git push origin vX.Y.Z
# .github/workflows/release.yml publishes to PyPI via trusted publishing

• v0.8.x — Current beta: 31 nano-services, 1167 tests, Ed25519 event provenance, RBI/DPDPA-aligned defaults.
• v0.9.0 — Planned: real PAN (NSDL/ITD) and Aadhaar (UIDAI) integrations; CKYC live lookup; CIBIL production keys.
• v1.0.0 — Planned: video KYC; e-NACH / UPI Autopay mandate collection; full RBAC; documented DR procedures; Docker images + Helm charts.

See CONTRIBUTING.md.

This project follows the Contributor Covenant v2.1.

Report vulnerabilities to sachncs@gmail.com — see SECURITY.md.

MIT © 2026 Sachin — not legal advice. Consult a qualified attorney before deploying in a regulated environment.