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async

  • Top-level await, and the module that blocks its importers

    Note1 min read

    A module using top-level await becomes asynchronous, and every module importing it waits — transitively. It is genuinely useful for conditional imports and for initialisation that must complete…

  • The retry that made the outage longer

    Deep dive16 min read

    A dependency recovered and went straight back down. Every client retrying at once, in lockstep, is a load test nobody scheduled.

  • Jitter matters more than the backoff curve

    Note1 min read

    Exponential backoff spreads a single client’s retries over time and does nothing about a thousand clients retrying in lockstep after one outage. The recovering-service failure is the one…

  • A CSV export that streams instead of collapsing

    Deep dive10 min read

    An export that worked until the account with 400,000 rows. fetchAll, a collection and a string built in memory, at 512 MB.

  • Queue priority is not a number, it is a separate queue

    Deep dive10 min read

    Password resets stuck behind a nightly export. A priority field does not help when the worker is already four minutes into something else.

  • A webhook endpoint that survives the sender

    Deep dive10 min read

    The payment provider retried for six hours and every attempt timed out. A webhook is a notification, not a request for processing.

  • A 202 with a status URL beats a request that waits

    Note2 min read

    An operation that takes ninety seconds does not fit in a request, and holding the connection open converts every timeout in the chain into a failure mode. The…

  • Promise.any resolves on the first success, not the first settle

    Note2 min read

    Promise.race settles on the first result including a rejection, and Promise.any waits for the first success. race is right for a timeout, where a rejection genuinely should win,…

  • A queue worker that stops cleanly

    Deep dive10 min read

    A deploy killed a worker mid-job and a customer was charged without an order. SIGTERM, a grace period that was too short, and the job that must be…

  • AbortController, and the fetch that outlived the component

    Note2 min read

    A fetch started in an effect keeps running after unmount, and its then sets state on a component that no longer exists. The abort rejects the promise with…