vocabulary:
  - term: QStash
    definition: >-
      Upstash's serverless message queue and task scheduling REST API that delivers
      HTTP messages to endpoints reliably using stateless HTTP requests, designed
      for serverless and edge runtimes.

  - term: Message
    definition: >-
      A discrete unit of data published to QStash for delivery to a destination
      URL. Messages are stored durably and delivered with automatic retry logic.
      Maximum size is 1 MB.

  - term: Destination
    definition: >-
      The target HTTP endpoint URL or URL Group name to which QStash delivers a
      message. Destinations must be publicly reachable HTTP APIs.

  - term: Publish
    definition: >-
      The act of sending a message to QStash via POST /v2/publish/{destination}.
      QStash accepts the message, stores it durably, and handles delivery
      asynchronously.

  - term: Dead Letter Queue (DLQ)
    definition: >-
      A holding area where messages are moved after exhausting all configured
      delivery retry attempts. DLQ messages can be inspected, republished, or
      deleted.

  - term: Schedule
    definition: >-
      A CRON-based configuration that causes QStash to deliver a message to a
      destination on a recurring basis. Schedules support standard CRON syntax
      and IANA timezone identifiers. Can be created up to one year in advance.

  - term: CRON Expression
    definition: >-
      A standard cron syntax string (e.g. "0 0 * * *") that defines when a
      scheduled message should be delivered. Timezone support is available via
      the CRON_TZ prefix (e.g. "CRON_TZ=America/New_York 0 4 * * *").

  - term: Queue
    definition: >-
      A named FIFO (first-in, first-out) buffer that ensures ordered message
      delivery to a destination. Queues support configurable parallelism for
      controlled throughput.

  - term: URL Group
    definition: >-
      A named collection of endpoint URLs. Publishing to a URL Group causes
      QStash to fan-out and deliver the message to all configured endpoints
      simultaneously (broadcast delivery).

  - term: Enqueue
    definition: >-
      The act of adding a message to a FIFO queue via POST
      /v2/enqueue/{queueName}/{destination} for ordered delivery.

  - term: Retry
    definition: >-
      Automatic reattempt of message delivery when the destination returns a
      non-2xx HTTP response or does not respond. Configurable via
      Upstash-Retries header (0-5 attempts).

  - term: Retry Delay
    definition: >-
      The waiting period between delivery retry attempts. Configurable via
      Upstash-Retry-Delay header using math expressions (e.g. "pow(2, retries)").

  - term: Callback
    definition: >-
      A user-specified URL (Upstash-Callback header) that receives an HTTP POST
      notification when a message is successfully delivered to its destination.

  - term: Failure Callback
    definition: >-
      A user-specified URL (Upstash-Failure-Callback header) that receives an
      HTTP POST notification when a message fails all delivery retries and moves
      to the DLQ.

  - term: Deduplication
    definition: >-
      A mechanism to prevent duplicate message delivery within a 10-minute window.
      Can be triggered manually via Upstash-Deduplication-Id header or
      automatically via Upstash-Content-Based-Deduplication header.

  - term: Delay
    definition: >-
      A configurable postponement of message delivery from when it is published.
      Set via Upstash-Delay header (e.g. "5m", "1h") or Upstash-Not-Before Unix
      timestamp.

  - term: Batch
    definition: >-
      A single API call to POST /v2/batch that publishes multiple messages at once
      to different destinations, URL Groups, or queues. Failed messages do not
      prevent other batch messages from being processed.

  - term: Flow Control
    definition: >-
      A mechanism to limit delivery parallelism and/or rate for a named key.
      Prevents overwhelming destination endpoints by capping concurrent deliveries
      and messages per time period.

  - term: Flow Control Key
    definition: >-
      A string identifier grouping messages under a shared flow control policy.
      Set via Upstash-Flow-Control-Key header when publishing.

  - term: Parallelism
    definition: >-
      The maximum number of messages delivered concurrently for a queue or flow
      control key. Defaults to 1 for queues; configurable per plan.

  - term: Rate Limit
    definition: >-
      A cap on the number of messages delivered within a time period for a flow
      control key. Enforced via rate and period settings.

  - term: Bearer Token
    definition: >-
      The authentication credential for QStash API requests. Obtained from the
      Upstash console and passed via Authorization header or qstash_token query
      parameter.

  - term: Upstash-Forward
    definition: >-
      A header prefix (e.g. Upstash-Forward-My-Header) used to forward custom
      headers to the destination. QStash strips the prefix before forwarding.

  - term: Global Parallelism
    definition: >-
      The maximum number of simultaneous in-flight message deliveries across the
      entire QStash account, bounded by the plan tier.

  - term: Message State
    definition: >-
      The lifecycle status of a QStash message. States include CREATED, ACTIVE,
      DELIVERED, ERROR, RETRY, CANCEL_REQUESTED, and CANCELLED.