1. Story and practice background

Immediately after deploying the order payment page, customer service centers were flooded with complaints. One customer was afraid that the money had already been deducted from the account and that sign-up approval had been missed, so he refused to pay when the English error message 'Error 1042: Transaction Declined by Carrier' suddenly appeared on the screen even though his card was only over the limit. Additionally, when the user impatiently pressed the payment button in a communication delay error situation, the same order approval query was sent to the database three times in succession, creating a serious data defect that resulted in double billing.

2. Learning objectives

• We can list four typical errors that occur during payment transactions, such as card limit exceeded, insufficient balance, and communication delay.
• Technical raw code can be replaced with friendly guidance text that erases customer anxiety and prescribes subsequent actions.
• Prevention rules can be designed to control double charging authorization attempts, such as button disables and idempotent order keys.

3. Download practice basic code

Copy or download the JavaScript/JSON skeleton source below and enter the local practice path (day9_raw_payment_errors.json) and save it.

json{
  "errors": [
    {
      "code": "ERR_CARD_LIMIT_EXCEEDED",
      "carrier": "PG_KCP",
      "description": "System transaction declined by external carrier due to lack of balance or limit exceeded on card"
    },
    {
      "code": "ERR_NETWORK_TIMEOUT",
      "carrier": "PG_TOSS",
      "description": "Network timeout occurred while communicating with toss payments gateway api"
    },
    {
      "code": "ERR_DUPLICATE_REQUEST",
      "carrier": "INTERNAL_GATEWAY",
      "description": "Idempotency validation failed. Multiple execution request of order id from same client detected"
    }
  ]
}

4. Codex AI Prompt Card

Copy and paste the prompt below into the AI question and answer window of Codex Client and receive guidance.

Based on the PG company's raw error log specification `day9_raw_payment_errors.json` provided, please create a friendly \'Korean guidance phrasebook for each error situation\' that never causes anxiety to users and a \'double authorization prevention response guideline (Mitigation Playbook)\' that blocks duplicate payment attempts.