Ultra-fast Serverless mode in Preview, with DeepSeek V4.1 Flash 1017 at 6-8x speed

Ultra-fast is a new high-speed Serverless mode, now in Preview, for highly latency-sensitive applications. Ultra-fast variants aim for 6-8x generation speed, and up to 10x for agentic coding tasks. Like Fast, it is not a different model, so output quality is the same.

Ultra-fast is available for DeepSeek V4.1 Flash 1017. To use it, set model to accounts/fireworks/routers/deepseek-v4p1-flash-1017-ultrafast. Priority tier is not available for Ultra-fast.

Ultra-fast is priced at a premium and has lower rate limits than the standard model. Preview modes are under active development and may change quickly. See Serverless Modes, Serverless pricing, and Serverless rate limits.