SPECIMEN 03 / sliding-expiry

The moving deadline

A retry quietly resets the clock.

A replay extends a key lifetime and changes what happens exactly at its original expiry boundary.

PUT THE TWO POLICIES SIDE BY SIDE

Same requests. Different memory.

LOCAL MODEL REPLAY

Walk through 4 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 moving deadline: 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 A · value A	Received	201receipt #1 · writes 1	201receipt #1 · writes 1
02	Tick 1key B · value B	Received	201receipt #2 · writes 2	201receipt #2 · writes 2
03	Tick 5key A · value A	Received	200receipt #1 · writes 2	200receipt #1 · writes 2
04	Tick 6key A · value A	Received	201receipt #3 · writes 3	200DIFFERSreceipt #1 · writes 2

WHAT MAKES THIS ONE TICK

A small failure, unpacked.

A is created at tick 0 and expires at tick 6 in this contract. The tick-5 replay must leave that deadline unchanged. The sliding-expiry model moves it to tick 11, so the tick-6 request replays an old receipt while the reference commits a new write.

Expiry behavior depends on the API contract: Stripe, for example, documents a retention period and how a key can be reused after pruning. Our fixed six-tick deadline is synthetic. A sliding lifetime is only a fault here because the declared contract requires a fixed one.

TAKEAWAYTest the deadline itself, and keep absolute timestamps when reducing the failure.

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.

Stripe API: Idempotent requests ↗

SPECIMEN LABEL / 03

Take it apart.
Take it home.

Evidence: Bundled model comparison
Operations: 4 finite synthetic steps
Fault: sliding-expiry
Boundaries: Keys A/B · values A/B · 6-tick expiry
Provenance: Authored learning fixture

Standalone Node test ↓Candidate JSON ↓Markdown explanation ↓

node --test sliding-expiry.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 vanished acknowledgment