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PAYMENTS ENGINEERING

Summary: Designed and built the platform's checkout and payments engines across 13+ payment integrations, card processors, cryptocurrency, alternative/wallet methods, gift cards, room-charge/folio posting, and house credit, behind a pluggable gateway abstraction, plus in-person hardware-terminal payments, a structured breakdown- reversing refund engine, dispute/chargeback management, a 30+ formula fee engine, and multi-source reconciliation.

Checkout

Description: Engineered checkout as an explicit state machine spanning cart, hold, payment intent, gateway response, and booking confirmation.

States: Cart → Hold → Payment Intent → Payment Response → Booking Confirmation.

Data Model

• Cart header + line items + a financial-tracking action record.
• Payment intent + payment items + an append-only payment log.
• Gateway response + confirmation records linking payment to the fulfilled booking/order.

Dual Engines

• A modern modular engine (clean cart / pay-intent / pay-response / pay-confirm / pay-log model, partner-commission and multi-order support).
• A legacy integrated engine retained for complex flows (terminal capture, preauth, external-inventory validation).

Processors

Description: Built and maintain a wide range of payment integrations, each implementing the operations relevant to its rails.

Card Processors

Stripe: Charge, auth + manual capture, refund, payment/setup intents, card-present, webhooks, multi-currency, marketplace (Connect).

Elavon: Terminal-socket charge, auth, refund over TLS; plus a dedicated 3D-Secure variant with full challenge/enrollment status handling.

Freedompay: Purchase, auth, and refund with merchant-defined metadata.

Shift4: Card-present processing with webhook ingestion.

Komoju: Card processing for the Japanese market (JPY), with tokenization and full/partial refund.

Crypto

Triplea: Cryptocurrency acceptance via hosted payment page + webhook confirmation; tracks crypto address/currency, receive amount, and hold/confirmed status.

Wallets And Alt Rails

• Digital wallets (Apple Pay / Google Pay) and alternative rails via the card-processor layer.
• ACH credit transfer and regional bank methods (SEPA debit, iDEAL, FPX).
• PayPal hosted checkout (OAuth2 token, capture-intent flow, webhook completion).
• Skipify-assisted and SMS-payment-link flows for remote/mobile payment.

Stored Value And Property

Gift Card: Gift-card balance authorization/redemption over an XML gateway protocol.

Room Charge: Guest-folio posting to a property system, OAuth token, room verification, charge posting, duplicate detection.

House Credit: House/property credit accounts, apply credit and refund-to-credit with root-transaction linkage.

Manual: Mark-as-manual/pending for offline/invoice/check collection.

Gateway Abstraction

Description: Designed a uniform gateway contract so processors are drop-in modules, the reason 13+ methods coexist cleanly.

Contract: Per-gateway {gateway}_create_intent / _cc_charge / _refund / _retrieve_intent / _cancel_intent (and prepare/preprocess/webhook where relevant).

Merchant Config: Per-merchant config (account id, keys, timezone, environment) selects and parameterizes the gateway.

Scale Problem: Merchant deduplication where many locations under one corporate entity share a single connected account, an in-memory processed-account set avoids duplicate API calls and rate limiting during bulk reconciliation.

Terminals

Description: Built hardware-terminal (card-present) payment support.

Capabilities

• Terminal/reader registration and location management against the processor.
• Card-present capture with a manual-capture workflow driven by a capturable-amount webhook and a bounded capture window.
• Kiosk/terminal identity, serial tracking, and multi-reader locations.

Card On File

Description: Built stored-payment-method / card-on-file support.

Capabilities

• Setup-intent tokenization without an immediate charge; off-session future-use flagging for recurring/subscription.
• Customer-profile linkage, billing-address capture, brand/expiry/last-four storage for display.

Fees

Description: Built a configurable fee/surcharge engine feeding the pricing breakdown (see COMP-03 / COMP-14).

Capabilities

• App fees (per-venue) and commission fees (per-partner-per-venue).
• 30+ formula variants: fixed, percentage, capped-percentage, per-guest, per-item, tiered, fixed-plus-percentage.
• Applied at cart projection and at final payment-intent computation, with per-ticket breakdown used by refunds.

Refunds Disputes Recon

Refund Engine

• Clones the original payment intent/items with negated amounts and recursively negates the itemized surcharge breakdown.
• Preserves the original charge and creates a mirror refund record for a complete audit trail.
• Full and partial refunds with per-surcharge selection; multi-hop refund unwinding along the original payment path (last-in-first-out).
• Role-gated refund-request workflow (request → review → approve → process) with PDF confirmations.

Disputes

• Dispute/chargeback lifecycle tracking (open / won / lost / closed) with evidence assembly from ticket, invoice, transaction, and customer data.

Reconciliation

• Tender, deposit, revenue, and adjustment reconciliation; processor-settlement reconciliation (gross vs. fees vs. net collected).

Non Card Types

Payment Types

• prepay
• comp
• invite
• partial
• no-show-fee

Webhooks Fulfillment

Webhooks

• Processor webhooks for intent-succeeded/failed, capturable-amount-updated, refunds, and dispute lifecycle, metadata-validated and livemode/environment-gated.
• Dedicated webhook handlers for crypto, SMS-payment, and card-present processors, with real-time socket notification on state change.

Fulfillment

• Invoice + ticket PDF generation (scannable QR), customizable per-context templates, and email delivery.

Cross Reference

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