Detailed component design

But due to time constraint I will cover the core services first and touch upon the other services at the high level.

Payment service:

This is the service which receives the payment event from checkout page.
A single checkout request have multiple orders each belonging to different seller.
The split of event to multiple orders takes place in this service.
First it logs the payment event in events_db and sends the individual order to order services.
This is the services that orchestrates the whole payment flow, which is response of updating the payment_status field in event_db once all the orders are completed successfully
It talks to Ledge service and Wallet service

Order Service:

Ledger Service:

Ledger services keeps track of double -entry book keeping that is it hold immutable entry of both debit and credit for a single transaction

Eg: user A - Debit $1

User B - Credit $1

At the end the total of this table has to be zero, if not auditing has to be raised.

This talks to ledger_db

Wallet Service:

This the service that maintains the account of seller balance. The sellers are not payed immediately once the order is placed, they are paid once the product is delivered.
The platform fee is deducted and rest to payed to seller something like monthly basis or when the seller raise a request for pay-out.
This service talks to wallet_db