Đối với các hệ thống thương mại điện tử, việc tích hợp với một cổng thanh toán trực tuyến (payment gateway) sẽ là yêu cầu cơ bản nhất, dịch vụ thanh toán này ngoài việc cần phải chính xác, chúng còn phải mang lại trải nghiệm tốt cho người sử dụng, xử lý được những sự cố có thể xảy ra trong quá trình thực hiện và đặc biệt là phải bảo mật. Đây là một bài toán khó về mặt kỹ thuật để có thể thiết kế và xây dựng một cách hiệu quả! Trong Techtalk #43 này, các bạn tham gia sẽ được chia sẻ về những thành phần của một payment gateway, quá trình xử lý một transaction, cách thức lưu trữ thông tin thanh toán, xử lý hoàn tiền,.. và những vấn đề gặp phải khác khi xây dựng một cổng thanh toán trực tuyến. Chủ đề sẽ đi qua các nội dung sau: - Payment Domain Knowledge - Payment Gateway Integration + Create Order + Check Order Amount (Optional) + Browser Redirect + Instant Payment Notification (IPN) + Payment Query (QueryDR) - Advance Concept + Tokenization + Credit Card Authorization/Reversal/Settle --- Ngôn ngữ: Tiếng Việt --- Speakers: - Nguyễn Văn Lợi - Technical Architect @ Vexere Anh Nguyễn Văn Lợi là một kỹ sư phần mềm với hơn 10 năm kinh nghiệm thực tế từ các công ty có hệ thống lớn trong các mảng VoIP, Ecommerce, Big Data, Logistics. Tại Vexere, anh luôn đề cao tinh thần tự học hỏi, phát triển và chia sẻ để team member liên tục tích lũy kiến thức, kỹ năng, nhằm tăng hiệu quả công việc và mang lại sản phẩm có trải nghiệm tốt nhất cho người dùng

1. Payment Gateway Demystified
December 11, 2021
Lợi Nguyễn - Technical Architect @ VeXeRe
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2. Vietnam’s largest online bus booking system
vexere.com
Self Introduction
Name: Lợi Nguyễn
Company:
● Vexere - #1 Saas based bus ticket platform in Vietnam
● Chotot - #1 Classified Marketplace in Vietnam
● Blue Orchid - A start-up founded by ex-Grab CTO
● Softfoundry - VoIP product
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3. Vietnam’s largest online bus booking system
vexere.com
Vexere Intro - SaaS Based Booking Platform
VeXeRe.com is a Vietnamese online bus ticket booking system that operates through
many transportation companies.
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4. Vietnam’s largest online bus booking system
vexere.com
Vexere Tech Stack
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5. Vietnam’s largest online bus booking system
vexere.com
Agenda
● Payment Domain Knowledge
● Payment Gateway Integration
○ Order Creation
○ Order Availability (Optional)
○ Browser Redirect
○ Instant Payment Notification (IPN)
○ Payment Query (QueryDR)
○ Lesson Learned
● Advance Concept
○ Tokenization
○ Credit Card Authorization/Reversal/Settle
● Q/A 5

6. Vietnam’s largest online bus booking system
vexere.com
What do you get after 2 hour?
Basic payment domain knowledge
Reliable payment service implementation
3 years lesson learned of integrating with 10 payment gateways for 4 business units @ Vexere

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vexere.com
Payment Domain Knowledge

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vexere.com
Internet Banking Payment API Flow

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vexere.com
Credit Card Payment API Flow

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Payment API Flow

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Simple Payment Integration
What problem could occur in this
integration flow?

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vexere.com
Simple Payment Integration
Problem could arises when:
● User close browser
● User’s network error

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vexere.com
Simple Payment Integration
Problem arises when connection
between client browser and
payment gateway:
● User close browser
● User’s network error

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vexere.com
Payment Gateway Integration

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vexere.com
Lesson Learned 1
How fast you can sync transaction status with others determine how good your payment
service is.
Implement 3 these API is required
● Redirect
● Instant Payment Notification (IPN)
● Polling (QueryDR)

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Lesson Learned 2
● Design your payment service for multiple tenant usage, standardize and
decouple:
○ Order creation API
■ Design an interface for many payment gateway/method (i.e. momo/zalo/onepay)
○ Order availability API
■ Design clear interface api response format, then use for all merchants.
○ IPN

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vexere.com
Lesson Learned 3
● Rate limit your IPN to external system (especially to critical system)
● Best practice: max retry is 5 times, sample:
○ Zalopay gateway: 3 times
○ VNpay: 5 times
○ Momo: 3 times
Sample: call to like airline booking system

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vexere.com
Tokenization
Problem:
● User input wrong card info: (top 6 reason of failed transaction)
○ Card number
○ Card holder
○ Issue/expire date
○ CVN number

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vexere.com
Tokenization

20. Vietnam’s largest online bus booking system
vexere.com
Tokenization
Problem:
● User input wrong card info: (top 6 reason of failed transaction)
○ Card number
○ Card holder
○ Issue/expire date
○ CVN number
● Recurring billing (i.e. electric bill)
Solution:
● Tokenization
○ Internet Banking Card Info
○ Visa/Master Card Info

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vexere.com
Tokenization

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Tokenization

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Tokenization - Demo

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Credit Card Authorization
Problem:
● Quick refund:
○ Normal visa/master transaction take 7-30 days for refund. Customer won’t be happy.
● Save cost of transaction fee:
○ 2-3% on transaction amount on transaction fee and refund fee.

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vexere.com
Credit Card Authorization
Problem:
● Quick refund:
○ Normal visa/master transaction take 7-30 days for refund. Customer won’t happy.
● Transaction fee:
○ 2-3% on transaction amount
Solution:
1. Authorization: Lock user account balance
2. Authorization reversal: Unlock user account balance
3. Settle: after user has started or finished their trip

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vexere.com
Credit Card Authorization
● Authorization refers to the process by which the business owner confirms that the customer
actually has funds available on their card to complete the transaction.
● Capture, on the other hand, refers to the process by which a transaction moves out of the pending
state and you get your money.
● Sale = Authorization + Capture

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vexere.com
Credit Card Authorization
● Credit Card popular transaction type is Sale, which charge user account balance
immediately
● But you can implement it differently, just lock user account some amount, then charge later
(i.e. after user finished using your service)

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Credit Card Authorization Refund

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Credit Card Refund
● Store authorization transaction id in DB
● Cronjob to scan & settle authorization older than 3-7 days
● Alert Slack when settle failed

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vexere.com
Demo
● Integrated with 10 payment gateway/wallet in Vietnam
● Integrated with 4 business units at Vexere
● Has 4 payment method:
○ Credit card payment
○ Internet banking payment
○ Wallet payment
○ QRCode

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Q&A
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Reference
● https://blog.clover.com/payment-gateway-vs-payment-processor-what-is-the-difference/
● https://home.bluesnap.com/snap-center/blog/global-payment-processor/
● https://docs.vexere.net/pages/viewpage.action?pageId=17205847
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Payment Terms
● Issuing bank - The customer’s bank that issued their credit card.
● Merchant - The business supplying goods or services for sale. This can be in-person or online.
● Merchant account - A merchant account is a special account that lets you accept and process digital
payments. This includes purchases made with credit or debit cards and other forms of electronic
payments.
● Acquiring bank - The bank that hosts the merchant’s credit card processing account.
● Payment processor - The service that sends transaction info between the merchant, the issuing bank,
and the acquiring bank.
● Payment gateway - The equivalent to a point of sale system for online transactions, it encrypts and
transmits information to the payment processor. A payment gateway provides integrations into
different e-commerce platforms and APIs to perform transactions. It also receives authorization for the
banks to move money from the customer to the merchant.
● Payment tokenization - The process of converting the customer’s card to another number to secure
their private information for the online purchase.

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vexere.com
Agenda
● Payment Domain Knowledge
● Payment Gateway Integration
○ Order Creation
○ Order Check (Optional)
○ Browser Redirect
○ Instant Payment Notification (IPN)
○ Payment Query (QueryDR)
● Advance Concept
○ Tokenization
○ Credit Card Authorization/Reversal/Settle
● Q/A
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Thank you <3
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● Software Engineer
● Product Manager
● Product UX Designer
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