What is Vercel's Fluid Computing?
"TLDR: This article provides an in-depth analysis of Vercel's Fluid computing technology, which addresses the cold start problem in traditional Serverless architectures through a mechanism similar to an operating system's thread pool. Its core lies in reusing already-created Node.js instances rather than frequently creating new ones, enabling features such as real-time scaling, resource pre-allocation, and pay-per-actual-usage billing, while also supporting advanced capabilities like streaming and post-response processing. The article points out that this design pattern closely resembles the resource scheduling strategies of computer operating systems, reflecting the innovative application of underlying systems engineering principles in the cloud-native domain."
Official article: https://vercel.com/blog/introducing-fluid-compute
Reddit discussion: https://www.reddit.com/r/nextjs/comments/1iibnj2/eli5_vercels_fluid_compute/?tl=zh-hans
Background
Vercel's Serverless computing has an inherent cold start problem. When a request comes in at any given moment, a Node instance needs to be created to handle it, and the cold start time is unavoidable. If a second request arrives immediately after, it might get lucky and hit the same already-created instance. If not, another Node instance needs to be created, resulting in another cold start.
Solution
Fluid Compute feels very similar to the thread pool commonly used in operating systems.
The original Serverless model is like a single thread in an operating system — when a task needs to be computed, a thread is created to handle it, and when another task comes in, another thread is created. The cost of frequently creating and destroying threads at scale is very high.
With a thread pool, you can significantly leverage idle threads to execute new tasks without needing to create new ones.
Mapping this to Serverless and Fluid Compute, it's about reusing previously created Node instances instead of repeatedly creating new ones — very similar in nature.
Corresponding to the features mentioned in Vercel's official article:
- Compute triggers only when needed
- Real-time scaling from zero to peak traffic
- Using existing resources before scaling new ones
- Billing based on actual compute usage, minimizing waste
- Pre-warmed instances reduce latency and prevent cold starts
- Supports advanced tasks like streaming and post-response processing
Many of these align with thread pool characteristics:
Thread pools also support scaling, reuse existing resources first, and support pre-warming.
Summary
These new features are essentially the common patterns used in computer operating systems.