Accept crypto payments in FastAPI (non-custodial, $0 fees)

Originally published on shieldz.cash.

Shieldz is a non-custodial crypto payment gateway: the buyer pays an address that belongs to you, funds settle straight to your own wallet, and there is no platform fee. Here is how to add it to a FastAPI app.

1. Create an invoice

from shieldz import Shieldz
from fastapi.responses import RedirectResponse

shieldz = Shieldz(os.environ["SHIELDZ_API_KEY"])

@app.post("/checkout")
def checkout():
    invoice = shieldz.invoices.create(amount_usd_cents=5000, memo="Order")
    return RedirectResponse(invoice["pay_url"], status_code=303)

The customer lands on a hosted checkout and pays with Bitcoin, USDC/USDT on five chains, or shielded Zcash.

2. Verify the webhook

Shieldz sends an HMAC-signed invoice.paid webhook. Verify the signature before fulfilling:

from shieldz import construct_event, SignatureVerificationError

@app.post("/webhooks/shieldz")
async def webhook(request: Request):
    raw = await request.body()
    try:
        event = construct_event(
            raw,
            request.headers.get("x-shieldz-signature", ""),
            os.environ["SHIELDZ_WEBHOOK_SECRET"],
        )
    except SignatureVerificationError:
        raise HTTPException(400)
    if event["type"] == "invoice.paid":
        ...  # fulfill the order
    return {"ok": True}

Why non-custodial

• $0 platform fee — you pay only network gas, never a percentage of sales.
• No custody — Shieldz only ever holds a public key, so there is nothing to freeze and nothing to skim. Verify it yourself.
• No KYC to start.

Full guide and API docs: Accept crypto in FastAPI and the API reference.