Mission 2 Practice Guide to Evaluating Service Quality
📥 Practice Input
- •
day5_signup_flow.md(DB physical schema definition)
💾 Practice output (Output)
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edge-case-analysis.md(Exception scenario report)
1. Story and practice background
On the first night of a startup's successful launch of its MVP product, an unexpected server alarm sounds. Two users pressed the payment button at the same time during the same reservation time slot, and both payments were successful, but only the last payer was overwritten in the database, and the reservation data of the first payer was lost. (Concurrency control exception situation)
The items of readability (information display), access operability, error response recovery, and flow efficiency are converted into objective scores based on international usability standards.
In this exercise, we will deliver the entire screen design and user movement to Codex, and build a quality report (Usability Evaluation) that includes a comprehensive score rating, painful design debt, and a supplementary action plan.
2. Learning objectives
- Logical design flaws can be detected in defined table schemas and foreign key reference structures.
- Edge case scenarios such as concurrent writing, operational accessibility (3.0/5.0) collapse, and transaction rollback failure can be derived.
- You can prepare countermeasures such as soft delete (logical deletion) to defend against hard delete withdrawal.
🛠️Practical guide to follow along
- Create file for practice: Click the download button below
day5_signup_flow.mdfileautomation/Save it within the folder. - Codex Verification Delegation: Build by sending the **Codex request prompt** below to the Codex Client prompt input window.
- Confirmation of response design: In the derived report, we review whether specific DB improvement measures, such as duplicate reservation prevention measures (distributed lock/unique constraints) and soft delete logical identifier design, have been established.
Download practice materials
Codex request prompt
Mission 02 Prompt
Based on the provided day5_signup_flow.md specification, please give a score out of 5 for each item such as 1) information readability, 2) operation accessibility, 3) error resilience, and 4) movement efficiency, and build a service quality evaluation (Usability Evaluation) that points out strengths and painful areas for improvement along with a comprehensive evaluation score.
4. Example results
Codex white-boxes the schema logic and derives the following fatal exception scenarios:
| Evaluation items | Detailed diagnosis and score (Edge Case) | system impact | Comprehensive improvement action plan (Action Plan) |
|---|---|---|---|
| Information readability (3.5/5.0) | A phenomenon in which two users make a reservation and payment at the same time during the same consultation time and both are judged successful, resulting in duplicate mapping. | fatal | Create complex UNIQUE constraints on DB reserved tables or apply Redis distributed locks |
| Accessibility to operation (3.0/5.0) | A phenomenon in which daily sales settlement statistics queries are broken due to the foreign key relationship being broken due to hard deleting of user records with payment history. | fatal | Changed Soft Delete (logical delete) table design to record is_deleted column and deletion time |
| Error resilience (2.5/5.0) | External PG payment approval was successful, but it was rolled back due to a network failure at the DB insert stage and the payment record was disassembled. | Normal | Bundle payment transactions into distributed transactions (Saga Pattern) and run a batch verification script for unconfirmed payments |