Use Cases


Get started today

Replay past traffic, gain confidence in optimizations, and elevate performance.

nylas logo
Speedscale Customers

Nylas improves account synchronization performance 30x with Speedscale


Nylas is a fast-growing SaaS technology vendor that helps companies synchronize email, calendar, contacts and other productivity data across thousands of accounts. With more companies working from home, their product usage has spiked, and they are building a next generation platform to handle additional use cases and scale. Over 26,000 developers use Nylas to send over 1 billion API requests per day to providers such as Gmail, Microsoft Exchange,, Yahoo! and more.


The company was facing a new (yet welcome) challenge they had not previously encountered—larger customers were signing on to use their platform, bringing higher integration loads with them. To prepare for the demands of these larger customers, David Ting, SVP of Engineering, was looking for a solution to help ensure uptime and stability.

In parallel, Nylas was also undergoing a migration from EC2 (an existing monolith application) to Kubernetes. The migration was required to accelerate release velocity, as well as provide the option to let customers deploy Nylas software on-premise. With the migration to Kubernetes, Nylas gained flexibility on how code was built and deployed, but a new set of challenges was introduced:

  • Each service team iterated independently, thus dependencies and connections grew
  • Applications required big rewrites to maximize microservice advantages
    While Kubernetes is elastic and self-heals, benchmarking individual APIs was difficult
  • Lack of control over third-party services, like Office365 and Google Apps
  • Difficulty maintaining the application during a shift in architecture (e.g. ongoing business, release schedules, and application quality)

Evaluating Solutions

Nylas’ requirements were for an easy-to-use platform that 1) supported their unique environment of Kubernetes and third party APIs with integrated TLS security and authentication, and 2) had an ability to record traffic and replay at scale. Having initially tried GoReplay, Nylas found that the frequency and changing data requirements were beyond the scope of what the open source tool was capable of.

It seems we can't find what you're looking for...

David ultimately made the strategic decision to implement Speedscale’s traffic replay in order to ensure performance parity in their migration to Kubernetes, as well as allow for fast iteration and tuning on their high-throughput APIs.

Using Speedscale

While moving from EC2 to Kubernetes, Speedscale’s traffic replay framework provided an easy-to-use interface for observing traffic and orchestrating and automating replays. By observing APIs, not only does Speedscale generate traffic replays, but mocks of critical dependencies as well. Within minutes, Speedscale was able to examine and ingest all of the inbound and outbound API calls across their service architecture. An initial set of recorded transactions could be expanded to represent 10K email accounts, and made available in a single container.

“Speedscale is a game changing capability that enables large architectural upgrades with quality. Traffic replay is high coverage and fast.”

Observing API traffic, generating snapshots and mocks, and replaying traffic was easily done through the dashboard and manifest files. Snapshot summaries and replay readouts were available during and after execution. Perhaps most importantly, orchestration of replay containers was handled by a Kubernetes operator and command-line for integration with CI tools and repeatable execution.

Nylas was able to improve account synchronization performance by 30x in just a few months.

Results & Future Outlook

Speedscale provided many benefits to the Nylas team, but chief among them was the ability to mock 3rd party endpoints at a scale unavailable anywhere else but production. With the availability of Office365 and Google Workplace mocks, the teams could rapidly iterate and validate at production volumes, with new versions of the sync, syncback, API, and dashboard services. This removed the need to create volumes of test data, because Speedscale orchestrated the dependencies and values for repeatable scenarios. The capability to shift-performance left was imperative to meet customer expectations and do so in a short timeframe.

On-demand Webinar

CNCF & Cimpress: Leverage User Traffic to Automate Load Testing this Holiday Season

As a result, Nylas was able to improve account synchronization performance by 30x in just a few months by using Speedscale.

The capability to shift-performance left was imperative for the Nylas team to meet customer expectations and do so in a short timeframe.