Meet the next iteration of JavaScript on Compute

Since the start, we built a JavaScript SDK that is both highly secure and performant by running the JavaScript virtual machine inside a WebAssembly sandbox. Compute’s isolation technology creates and destroys a sandbox for each request flowing through our platform in microseconds. This technology holistically minimizes attack surface area while maintaining the ability to scale and perform, and keeps your code completely isolated from other requests flowing through the platform. 

From this JavaScript SDK beta launch, we’ve learned that JavaScript on Compute is performing on par with our competitors in certain application workloads but not all, and it trails behind our Rust SDK counterpart. Today we’re happy to announce that we’ve made several improvements to Compute that substantially boost the performance of the JavaScript runtime, as well as the overall developer experience on the platform. 

With these improvements, we’re excited to announce the latest release of our JavaScript SDK, supporting full production use. Let’s explore what’s new.

Improved compute performance

We’ve improved raw performance on running our customers’ code by applying a number of key changes. For example, we switched from using the Lucet WebAssembly runtime to Wasmtime, which has undergone many performance optimizations over the last two years. 

We also developed a more efficient mechanism for scheduling workloads, significantly reducing the scheduling overhead. This change is particularly important for JavaScript performance, leading to a doubling of performance for most JavaScript workloads.

Reduced overhead for creating service instances

In addition to running your code as fast as we can, there’s another key aspect to maximizing performance: how quickly we get to the point of executing it after a request comes in. We’ve made significant improvements to our platform to reduce the overhead of creating new service instances. As a result, you’ll experience faster time to first byte, or TTFB.

Reduced variability in instantiation time

We’ve also enhanced how our operating system handles the way memory gets reclaimed when a service hasn’t been used for awhile. The changes we applied greatly eliminated delays for all subsequent service instantiations after the first. 

Additional functionality

The above changes improved the Compute platform as a whole, and the JavaScript SDK as well as our other supported languages benefited as a result. However, for the JavaScript developer experience, we add these new functionalities to the latest release to support full production use:

Find out more

Developers are building interesting — not to mention performant — things on Compute using the JavaScript SDK. One ecommerce company increased its SEO rankings by maintaining highly performant redirects served from the edge by removing the load of processing from origin servers. A media delivery company is using it to conduct dynamic ad insertion on the fly, resulting in a highly personalized and low-latency experience for their end users.

For more information on how to get started with the JavaScript SDK, check out our documentation and example codes on Developer Hub. And if you’re not yet using our serverless platform, explore Compute in depth for free.

Christine Cole
Senior Product Manager

3 min read

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Christine Cole
Senior Product Manager

Christine Cole is a senior product manager at Fastly, where she is responsible for Compute@Edge. Prior to Fastly, Christine led various data platform product initiatives solving interesting Big Data processing challenges for CDNs and Signal Sciences. When not working, she can be found jogging by the beach while listening to audiobooks, cooking up interesting recipes, and keeping her kids entertained with various crafts.

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