SPECIMEN 04 / forget-on-loss

The vanished acknowledgment

The response disappears. The write stays.

A lost response incorrectly erases deduplication state, so recovery commits the same intent again.

PUT THE TWO POLICIES SIDE BY SIDE

Same requests. Different memory.

LOCAL MODEL REPLAY

Walk through 5 authored operations. The first visible difference appears at operation 4. Playback illustrates fixed evidence; it does not run an agent or contact a service.

The complete evidence

Always available below, with or without playback.

The vanished acknowledgment: fixed reference and faulty observations. Write counts are cumulative; a dash means no receipt reached the caller.
Operation	Request	Delivery	Correct reference	Faulty policy
01	Tick 0key B · value B	Received	201receipt #1 · writes 1	201receipt #1 · writes 1
02	Tick 1key A · value A	Lost after commit	Response lostreceipt — · writes 2	Response lostreceipt — · writes 2
03	Tick 2key B · value B	Received	200receipt #1 · writes 2	200receipt #1 · writes 2
04	Tick 3key A · value A	Received	200receipt #2 · writes 2	201DIFFERSreceipt #3 · writes 3
05	Tick 4key B · value A	Received	409receipt — · writes 2	409DIFFERSreceipt — · writes 3

WHAT MAKES THIS ONE TICK

A small failure, unpacked.

The A request at tick 1 commits before its response is lost. Neither caller sees a status or receipt, but both models have committed two writes. At tick 3, the reference recovers receipt 2; the forget-on-loss model has discarded the key and commits a third write.

AWS describes the uncertainty a caller faces when a creation request receives no response. Here, delivery loss occurs after the modeled service finishes. That boundary makes a specific question testable without simulating a real network or claiming a crash-safety result.

TAKEAWAYAn absent acknowledgment is not evidence that an operation failed. Recovery should preserve the original intent.

Read the foundations

These sources explain the underlying retry and idempotency concepts. This exhibit is an authored model example, not a claim that a source or vendor contains this fault.

AWS Builders’ Library: Making retries safe with idempotent APIs ↗

SPECIMEN LABEL / 04

Take it apart.
Take it home.

Evidence: Bundled model comparison
Operations: 5 finite synthetic steps
Fault: forget-on-loss
Boundaries: Keys A/B · values A/B · 6-tick expiry
Provenance: Authored learning fixture

Standalone Node test ↓Candidate JSON ↓Markdown explanation ↓

node --test forget-on-loss.test.mjs

Runs the bundled models locally by default, with no account or network request. To check your implementation, use BUG_ZOO_ADAPTER and the local adapter instructions. Your selected adapter runs with your permissions. The seven-case test kit covers more of the contract. Download asset license: MIT.

THE NEXT MOVE IS YOURS

Can you make it smaller?

This fixture includes removable work. Load it in the contribution workbench, select an operation to remove, and check whether the failure survives. Checking is free of publication; a public contribution requires your deliberate consent.

Remix this specimen ↗Build on an accepted result ↗

An exhibit has no parent receipt. Start from an open handoff to extend an accepted artifact with its exact attribution.

A different failure or interpretation?Bring your own synthetic case ↗Discuss the policy ↗Continue saved work ↗

MEET THE NEXT SPECIMENThe double-tap write