Transaction Flows & Message Matching Quiz

1. Your terminal sends an authorization request (0100) with STAN=123456. After 30 seconds with no response, what should the terminal do FIRST?

Retry the 0100 with the same STAN Send a reversal (0400) with a NEW STAN Send a reversal advice (0420) with the same STAN Assume the transaction failed and notify the merchant

2. What is the correct matching key used to link an 0110 response to its 0100 request?

DE37 (RRN) alone DE11 (STAN) alone DE11 (STAN) + DE12 (Local Time) + DE32 (Acquirer ID) DE2 (PAN) + DE4 (Amount)

3. What is the fundamental difference between a 0400 (Reversal Request) and a 0420 (Reversal Advice)?

0400 is for full reversals, 0420 is for partial reversals 0400 asks permission to reverse, 0420 declares the reversal happened 0400 is sent by acquirers, 0420 is sent by issuers 0400 uses DE90, 0420 does not

4. You're building a reversal (0400) for an original authorization. Which statement about DE90 (Original Data Elements) is correct?

DE90 should be built from the 0110 response fields DE90 should be built from the original 0100 request fields DE90 contains the STAN from the reversal itself DE90 is optional and only used for partial reversals

5. A terminal sends 0100, receives 0110 with DE39='00' (approved), but crashes before printing the receipt. After restart, it sends 0400. The 0410 response has DE39='12' (Invalid transaction). What likely happened?

The original 0100 was never received by the issuer The original authorization was already posted/settled, not just pending The reversal had an incorrect DE90 The STAN in the reversal was wrong

6. What is the purpose of Network Management message 0800 with DE70='301'?

Sign-on to the network Key exchange request Echo test (keep-alive) End-of-day cutover

7. A Financial Advice (0120) is different from an Authorization Request (0100) because:

0120 can only be used for refunds 0120 is a notification that the transaction already occurred (store-and-forward) 0120 doesn't require a response 0120 is used for network management

8. You observe this sequence in production logs: 14:30:45 - Sent 0100 (STAN=123456) 14:31:15 - Timeout, sent 0400 (STAN=123457) 14:31:16 - Received 0110 (STAN=123456, DE39=00) What should the system do with the late 0110?

Process it normally - the transaction was approved Cancel the pending reversal and process the approval Log it and ignore it - the reversal is already in progress Send a new reversal for this late response

9. What fields in a 0400 reversal MUST have NEW values (not copied from the original 0100)?

DE2 (PAN) and DE4 (Amount) DE11 (STAN) and DE7 (Transmission DateTime) DE37 (RRN) and DE38 (Auth Code) DE32 (Acquirer ID) and DE41 (Terminal ID)

10. A terminal has sent 3 reversal requests (0400) and all have timed out. According to typical timeout handling, what should happen next?

Continue sending 0400 indefinitely Give up and mark the transaction as 'unknown' Send a Reversal Advice (0420) declaring the reversal Escalate to manual intervention immediately

11. Why is STAN uniqueness per terminal per day critical for message matching?

It's required by PCI DSS security standards It prevents matching a response to the wrong request It's used to calculate the MAC (message authentication code) It determines the transaction sequence for settlement

12. In a partial reversal scenario (pre-auth $100, actual charge $80), what should DE4 contain in the 0400 reversal message?

The original pre-auth amount ($100.00 = 000000010000) The actual charged amount ($80.00 = 000000008000) The amount being released ($20.00 = 000000002000) The difference as a negative value

13. Which statement about the relationship between 0120 (Financial Advice) and 0121 (Financial Advice Repeat) is correct?

0121 is sent when the 0120 is declined 0121 is a retry of 0120 when no 0130 response is received 0121 has different fields than 0120 0121 indicates the transaction was reversed

14. A Visa transaction uses DE11 + DE7 for matching, while a local network uses DE11 + DE41. How should a payment gateway handle this?

Always use the strictest matching (all fields) Use a configurable MatchingStrategy based on the network routing Only match on DE11 since that's common to both Require all networks to use the same matching rules

15. You're debugging a production issue where customers see double charges. Investigation shows: Tx1: STAN=123456, Time=14:30:45, RRN=240315000001 Tx2: STAN=123456, Time=14:30:45, RRN=240315000002 Both approved, same amount, same card. What's the most likely root cause?

The issuer processed the transaction twice The terminal's STAN generator has a race condition Network duplicate detection failed The matching key is incorrectly configured