> ## Documentation Index > Fetch the complete documentation index at: https://arklowdocs.io/llms.txt > Use this file to discover all available pages before exploring further. # Lanes A lane is the unit of dispatch control: one destination, one combination of tag values, within your org. Every lane holds its own limits. ## Tags Tags create lanes. For example, an action tagged `{"region": "eu"}` and an action tagged `{"region": "us"}` dispatch through different lanes of the same destination. An action with no tags dispatches through the destination's default lane. Tags come from: * The ingress body's `tags` field. * `tag.` query parameters on ingress. * A [rule](/resources/rules/index) with the **Assign Tags** effect. ## Isolation Lanes adjust independently. A tenant overwhelming the `{"customer": "acme"}` lane has no effect on the limits of `{"customer": "initech"}`. Tag by dimensions that separate failure domains, such as tenant or region. ## Limits Each lane carries two limits: * **Running limit**: the number of deliveries in flight. * **Unsettled limit**: the number of deliveries awaiting settlement. The limits start conservative and follow the destination. ## Caps A cap pins a lane below what it would otherwise run at. The lanes API accepts a running cap and an unsettled cap, and the engine treats each as a ceiling. A running cap of `0` pauses the lane. ## Cardinality Tags are for dimensions with a small set of values. An action definition can spread across a **maximum of 1000 lanes**. Ingress rejects work that would create more with `TAG_CARDINALITY_EXCEEDED`. ## Reference