> ## Documentation Index > Fetch the complete documentation index at: https://openrouter.ai/docs/llms.txt > Use this file to discover all available pages before exploring further. # ChatRequestServiceTier The service tier to use for processing this request. `fast` is accepted as an alias for `priority`. ## Example Usage ```go theme={null} import ( "github.com/OpenRouterTeam/go-sdk/models/components" ) value := components.ChatRequestServiceTierAuto // Open enum: custom values can be created with a direct type cast custom := components.ChatRequestServiceTier("custom_value") ``` ## Values | Name | Value | | -------------------------------- | -------- | | `ChatRequestServiceTierAuto` | auto | | `ChatRequestServiceTierDefault` | default | | `ChatRequestServiceTierFast` | fast | | `ChatRequestServiceTierFlex` | flex | | `ChatRequestServiceTierPriority` | priority | | `ChatRequestServiceTierScale` | scale |