Serverless Modes

Fireworks Serverless offers three modes:

Standard is the default mode. No service_tier parameter is needed.
Priority tier is for workloads that require higher reliability during peak traffic.
Fast is for workloads that require higher speeds.
Ultrafast (Private Preview) for workloads requiring extremely fast end-to-end generation speeds.

Priority tier

Priority tier is for workloads that require higher reliability during peak traffic periods, at a higher price point. Priority tier is prioritized above Standard traffic and is less likely to be load shed (503 server overloaded). To use priority tier, set service_tier to "priority". Supported on OpenAI-compatible chat completions and on the Anthropic-compatible messages API:

curl https://api.fireworks.ai/inference/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $FIREWORKS_API_KEY" \
  -d '{
    "model": "accounts/fireworks/models/glm-5p3",
    "service_tier": "priority",
    "messages": [{"role": "user", "content": "Hello"}]
  }'

Priority tier is available on select models. Models and pricing are listed on the Serverless pricing page.

Fast

Fast is a high-speed mode, useful for interactive applications that require fast response speeds, at a higher price point. Fast variants aim for 100+ tokens per second of generated throughput. It is not a different model and the quality of the model remains the same. Fast is available for select models. To use Fast, change the model ID as listed below.

Model	`model` ID
Kimi K3 Fast	`accounts/fireworks/routers/kimi-k3-fast`
GLM 5.3 Fast	`accounts/fireworks/routers/glm-5p3-fast`

curl https://api.fireworks.ai/inference/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $FIREWORKS_API_KEY" \
  -d '{
    "model": "accounts/fireworks/routers/kimi-k3-fast",
    "messages": [{"role": "user", "content": "Hello"}]
  }'

Pricing is listed on the Serverless pricing page.

Ultrafast (Private Preview)

Ultrafast is a high-speed mode, useful for extreme latency sensitive applications that require fast response speeds, at a higher price point. Ultrafast variants aim for 1500+ tokens per second of generated throughput for agentic coding tasks. It is not a different model and the quality of the model remains the same. Ultrafast is in Private Preview and is available for the models listed below. To get access to Ultrafast please reach out to the team here. Once access is granted, change the model ID as listed below.

Model	`model` ID
Deepseek V4.1 Flash 1017	`accounts/fireworks/models/deepseek-v4p1-flash-ultrafast`

curl https://api.fireworks.ai/inference/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $FIREWORKS_API_KEY" \
  -d '{
    "model": "accounts/fireworks/routers/deepseek-v4p1-flash-ultrafast",
    "messages": [{"role": "user", "content": "Hello"}]
  }'

Serverless overview
US-only Serverless
Serverless quickstart
Text models
Anthropic compatibility — service_tier is supported on both OpenAI-compatible chat completions and the Anthropic messages API.

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Priority tier

Fast

Ultrafast (Private Preview)

​Priority tier

​Fast

​Ultrafast (Private Preview)

​Related

Priority tier

Fast

Ultrafast (Private Preview)

Related