Artificial Intillegence » Zelle Payment for evergreen

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Client App → Payments API → Payment Orchestrator
↓
Bank Client (httpx → Bank Partner API)
↓
Bank Partner (Zelle rails)
↓
Counterparty Bank/Zelle
↓
Webhook Receiver (FastAPI)
↓
Payment Orchestrator (update status)
↓
Observability (metrics + logs)

1. Payment Orchestrator

Role: Central brain for initiating and managing payments.

Responsibilities:

Accepts a payment initiation request (e.g., {amount, recipient, client_ref}).

Generates a payment_id (UUID).

Calls Bank Client to send payment to partner bank’s API.

Tracks lifecycle states: initiated → processing → completed/returned.

Handles retries (e.g., if partner bank API is down).

Persists state to database (payments table).

2. Bank Client (httpx)

Role: Abstraction over the partner bank’s Payments API.

Responsibilities:

Handle auth (OAuth2, mTLS, API key depending on Chase/partner requirements).

Send payment initiation requests via HTTP.

Map responses to internal schema (payment_id, status, bank_ref).

Include resiliency: timeout, retries, circuit breaker (httpx supports retries).

Example:

async with httpx.AsyncClient() as client:
resp = await client.post(
bank_url + "/payments",
headers={"Authorization": f"Bearer {token}"},
json=payload
)

3. Webhook Receiver (FastAPI)

Role: Handle async notifications from bank/Zelle (e.g., payment completed, returned).

Responsibilities:

Expose /webhook/payments.

Verify auth/signature from partner bank.

Parse payload and update local DB (payment_id, status, timestamps).

Ack quickly with 200 OK.

Queue heavy processing (e.g., ERP updates) to async workers.

Example (FastAPI):

from fastapi import FastAPI, Request

app = FastAPI()

@app.post("/webhook/payments")
async def payment_webhook(req: Request):
body = await req.json()
payment_id = body["payment_id"]
status = body["status"] # Update DB with new status
return {"ok": True}

4. Observability

Logs:

Every log line includes payment_id and client_ref.

Example:

{"level":"info","payment_id":"1234","client_ref":"INV-1002","msg":"Payment initiated"}

Metrics (Prometheus / OpenTelemetry):

payment_status_total{status="initiated"}

payment_status_total{status="completed"}

payment_status_total{status="returned"}

payment_retry_count{payment_id="1234"}

payment_webhook_latency_seconds{}

Tracing (OpenTelemetry + Jaeger/Tempo):

Trace spans: PaymentOrchestrator → BankClient → WebhookReceiver.

Propagate payment_id + client_ref as trace attributes.

🔹 Payment Lifecycle Example

Initiation:
Client → Orchestrator → Bank Client → Bank API → initiated.
Log: {"payment_id":"123","status":"initiated"}

Webhook:
Bank → Webhook Receiver → DB update → Orchestrator marks completed.
Log: {"payment_id":"123","status":"completed"}

Metrics:

payment_status_total{status="initiated"}++

Later payment_status_total{status="completed"}++

Webhook latency recorded.

🔹 Suggested Tech Stack

FastAPI → Orchestrator + Webhook service.

httpx → Bank client.

SQLAlchemy / Postgres → Persistence for payments.

Celery / RQ → For async retries & background jobs.

Prometheus + Grafana → Metrics.

OpenTelemetry + Jaeger → Tracing.

Structured JSON logging → For correlation.