> ## Documentation Index > Fetch the complete documentation index at: https://docs.basaltic.sh/llms.txt > Use this file to discover all available pages before exploring further. # Queue > Send, lease, and acknowledge messages with standard and FIFO queues. Queue holds messages until a consumer processes and acknowledges them. Use standard queues for at-least-once delivery with best-effort ordering, or FIFO queues for ordered processing within each message group. The service is regional. The endpoint for São Paulo is `https://queue.sa-saopaulo-1.basaltic.sh`. Calls use a bearer token and the account handle in `X-Account-Id`; see [Authentication](/authentication). ## Receiving is a lease Receiving hides a message for the visibility timeout and returns a receipt handle. Delete the message with that handle when processing succeeds. If the lease expires first, the message becomes available again. A new receive returns a new handle; an expired handle cannot acknowledge another consumer's lease. Use the visibility endpoint to extend or shorten a current lease. The peek endpoint is a separate operation and permission: it inspects messages without leasing them. ## Queue contracts | Contract | Behavior | | - | - | | Standard | At-least-once delivery and best-effort ordering. Consumers must tolerate redelivery. | | FIFO | The name ends in `.fifo`; ordering is within `message_group_id`. The queue type is fixed at creation. | | Long polling | `wait_time_seconds` waits up to 20 seconds for a message. | | Acknowledgment | Delete with the receipt handle from the current lease. | | Encryption | Message bodies are encrypted at rest. A customer KMS binding uses `kms_key`. | Queue responses expose customer-managed encryption as a `kms_key` resource reference with `id`, `crn`, and `name`. Platform encryption omits that field. If the key's metadata is unavailable, its reference retains the stored ID and CRN without a name. This does not switch the queue to platform encryption. A queue's `redrive_policy.dead_letter_queue` is a resource reference with the target queue's `id`, `crn`, and `name`. Create and update requests still accept a UUID, name, or CRN string in that field. `max_receive_count` controls when a message moves to the target. On updates, omitting `kms_key` or `redrive_policy` preserves the current value. Send `kms_key: null` to restore platform encryption for future messages, or `redrive_policy: null` to remove the dead-letter policy. Existing messages keep the encryption key that sealed them. ## Metrics Open a queue's **Metrics** tab for queue depth, message traffic, oldest available message age, and stored payload. Use the time-range controls to compare changes over time. The same series are available through [Telemetry](/telemetry#metrics) and can be used in metric alerts. Series are sampled every 30 seconds and carry `queue_id` and `region` labels. Reads require `telemetry:ReadMetrics` in the selected account and region. On FIFO queues, an earlier message in the same group can still block receiving a message counted as available. | Metric | Type | Meaning | | - | - | - | | `basaltic_queue_messages_available` | Gauge | Unexpired messages whose visibility time has elapsed. | | `basaltic_queue_messages_in_flight` | Gauge | Unexpired messages with an active visibility lease. | | `basaltic_queue_messages_delayed` | Gauge | Unexpired messages whose initial delay has not elapsed. | | `basaltic_queue_stored_bytes` | Gauge | Payload bytes in unexpired messages. | | `basaltic_queue_oldest_available_message_age_seconds` | Gauge | Time since enqueue of the oldest available message; zero when empty. | | `basaltic_queue_messages_enqueued_total` | Counter | Stored messages, including arrivals from redrive; deduplicated sends are excluded. | | `basaltic_queue_messages_received_total` | Counter | Message leases, including redeliveries. | | `basaltic_queue_messages_removed_total` | Counter | Removals through acknowledgement, expiry, purge, or redrive. | | `basaltic_queue_bytes_enqueued_total` | Counter | Payload bytes accepted into the queue. | Use `last` for current depth and `rate` for per-second traffic. Counters start when this metrics feature is deployed and persist through message deletion and worker restarts. Earlier traffic is not backfilled. An idle queue emits zero gauges; a missing observation leaves a gap instead of reporting zero. Choose type, timing, encryption, and a dead-letter destination. Lease messages, extend visibility, and acknowledge processing. Control ordering and isolate repeated failures. Separate producers, consumers, and queue administrators. This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.