📌 Part 1. Introduction background and need for education
Payment is not simply a technical module that receives money, but a psychological act in which the user pays. Before mechanically implementing linkage with external PG companies, purchase rate can be protected by maximizing movement convenience and financial trust from the user's perspective. In this session, you will learn how to cut out complex multi-level exit barriers through Codex Workspace, replace error codes such as limit exceeded and waiting for communication with safe Korean text, and segment receipts and place security badges.
1. Three major frictions to overcome when designing payment services
- Fatigue due to multi-step payment flow: Users give up on payment due to too many procedures such as entering delivery address, authentication, and selecting method.
- Unfriendly and unclear error feedback: It only emits a raw error code (`Error 1042`, etc.) and does not explain whether or not the withdrawal was made, which frustrates the user.
- Lack of trusted devices and information visibility: The display of VAT inclusion and detailed discount are vague, and there is no refund link, which leads to hesitation and withdrawal right before payment.
2. Comparison of the gap with general AI use
| performance area | General AI (Interactive Browser) | Codex Workspace (working directory linkage) |
|---|---|---|
| Payment flow analysis | Explains only the general order-payment API communication protocol sequence | Simplify by reading `day9_current_checkout_flow.md` to pinpoint duplicate identity verification requests and address form loss sections. |
| Establishing error feedback | “Change errors kindly” level advice | Return of Korean text containing user action actions for each code of the raw error code (`day9_raw_payment_errors.json`) and measures to prevent duplicate attacks (disabled) |
| Payment UI Audit | General UI design grid guide | Read `day9_payment_ui.html` and return revised HTML with detailed discount receipt style separator, security text, and refund link applied. |
📌 Part 2. Practice outcome mapping relationship
Upon completing the training, the following five core plans and patch source codes will be built in your local workspace.
- Task 01:
day9_optimized_flow.md- Order payment flow simplified to 3 steps by eliminating pop-ups - Task 02:
day9_error_mitigation_guide.md- Safe Korean text for each error code and guide to prevent double requests - Task 03:
day9_robust_payment_ui.html- Revised UI with detailed deduction receipt and security 🔒 mark applied - Mission 01:
day9_failure_scenarios.md- PG window closing and inspection response response message collection - Mission 02:
day9_checkout_journey.md- Block initialization of input form when coupon modal is focused. Journey diagnosis certificate
📌 Part 3. User-safe payment process structure diagram
This is an on-screen trust journey flow that prevents user churn and provides trust.
📌 Part 4. Practical Application Tips (Best Practices)
1) Transaction Idempotency:
When the payment transmission flag `isPending` is true, clicks are disabled and blocked at the source, and the unique UUID `orderToken` for each order is thrown to the PG company as an identifier to block double billing due to repeated user hits.
2) Price Breakdowns:
Users are more likely to be convinced of the legitimacy of the transaction when it is expressed in detail as 'Basic fee KRW 50,000 - Launch special discount KRW 10,000 = Final actual payment amount KRW 40,000 (VAT included)' rather than just a single line 'Subscription amount KRW 50,000'.
📌 Part 5. Instructor guidance (topic of discussion)
- Simple payment fees vs. churn mitigation: Naver/Kakao simple payment fees are higher than regular cards, but they dramatically reduce churn. Should early startups prioritize defending fees or subscription payment success rates?
- Measures against payment wireless network failure: If money goes out from the server but the user's phone fails to receive notifications because the screen turns off, what post-recovery route is the best solution to prevent customer service intrusion?