Distinguish duration and idle TTL — Build the smallest useful slice

PART I

Warm-up

Reconnect with a useful idea before starting distinguish duration and idle ttl. In one or two sentences, describe the input, output or host boundary from the previous exercise that this lesson builds on. If you are arriving directly, skim the worked example first; there is no locked prerequisite.

A rough note is enough. You can revise it after the example.

PART II

Instruction & guided example

Calculate idle expiry with explicit refresh

A second cache uses a 30-minute idle policy. The supplied host contract says successful reads refresh last access. Creation is 10:00; successful reads are 10:10 and 10:25.

Initial expiry is 10:30. Read at 10:10 moves it to 10:40; read at 10:25 moves it to 10:55. A denied read at 10:45 does not refresh under this contract. The source mentions refreshOnAccess but does not define every access event, so this exercise states which events qualify instead of pretending the source resolved it.

Use the supplied case as a paper design exercise. WillowScript and these library integrations are proposed and unimplemented here; no interpreter or native host has checked the example. Preserve the source API spellings, label new policies as exercise-host contracts, and distinguish a predicted result from measured execution.

Worked reasoning and supplied artifact

// PAPER FIXTURE — Calculate idle expiry with explicit refresh
// Manual worked artifact; comments below are not executable source.
// INPUT / CONTRACT: A second cache uses a 30-minute idle policy. The supplied host contract says successful
// reads refresh last access. Creation is 10:00; successful reads are 10:10 and 10:25.
// DERIVATION / EXPECTED ARTIFACT: Initial expiry is 10:30. Read at 10:10 moves it to 10:40; read at 10:25
// moves it to 10:55. A denied read at 10:45 does not refresh under this contract. The source mentions
// refreshOnAccess but does not define every access event, so this exercise states which events qualify
// instead of pretending the source resolved it.

Illustrative example from the proposed WillowScript design. The language and WUIX/WMATH/WDB/WAUDIO/WTMP services are not implemented in the supplied source. This site has no interpreter, VM or native host and does not execute or certify the snippet.

Try the guided change

Reconstruct the supplied worked case first: list its inputs, intermediate decisions and final artifact. Compare each row with the explanation and identify exactly where the rejected alternative fails. Then use the changed inputs in Part IV for independent work.

• Write the supplied inputs and initial state before following the example.
• Reconstruct each intermediate calculation or host decision, then compare with the worked artifact.
• Explain why the contrasting alternative fails before attempting the changed inputs in Part IV.

PART III

Take a breather

Step back after the guided example. Look away from the screen, stretch, or reread your prediction. This is an optional learning pause, not a timer or an assessment gate.

When you return, try to name the lesson’s key idea without copying its wording. If that feels difficult, return to Part II and trace one line rather than restarting the entire lesson.

PART IV

Independent practice

Project context: Bounded report cache. Build a small, understandable change around distinguish duration and idle ttl.

Trace successful read 12:05, denied read 12:20 and successful read 12:30 for an entry created 12:00. Mark whether expiry had already occurred before each event.

What to produce

Trace successful read 12:05, denied read 12:20 and successful read 12:30 for an entry created 12:00. Mark whether expiry had already occurred before each event.

• State the intended behavior in a sentence before editing.
• Use only source-backed syntax and the host services whose contract you have been given.
• Record a normal case and a boundary or unavailable-resource case.
• Label hand predictions separately from anything actually measured in a supplied toolchain.

Syntax colors are a reading aid, not a compiler. The line you are editing stays uncolored until you move to a different line; capitalization is never changed. Drafts stay on this browser and code is not executed.

import tmp;
const cache = tmp.create({
    name: "report-cache",
    storage: "ssd",
    maxSize: "2GB",
    lifetime: { duration: "30m", refreshOnAccess: true },
    cleanup: { automatic: true, onCrashRecovery: true }
});

PART V

Self-check

Use this check to notice what to revisit. It does not award a private course grade, block another page or claim to verify compiled code. Every answer has a learning explanation.

You may keep exploring even if you are unsure. Use the hint, compare the trace, and revise your explanation.

PART VI

Recap & small task

Bring the idea back to the mod feature you are building. A useful recap connects the mechanism to a decision you can make in your own code.

• Calculate idle expiry with explicit refresh
• A second cache uses a 30-minute idle policy. The supplied host contract says successful reads refresh last access. Creation is 10:00; successful reads are 10:10 and 10:25.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

Explain why “11:15” fails for the supplied case, then give one changed input that would require revisiting your conclusion.

This marks your personal practice record only. It is not a certification or an official workspace assessment.