Business continuity at Slack: Keeping our customers up and running during Covid-19

Author: Cal Henderson, co-founder and CTO, and Robby Kwok, Senior Vice President, PeopleMarch 6th, 2020

Whether you’re using Slack already, or are considering Slack to help you manage remote work under the current circumstances, we want you to know that Slack has comprehensive plans in place to ensure we remain up and running.

Many of you are looking to Slack to uphold your business continuity plans—whether your offices have closed or might close in the future, or perhaps your employees are working from home or can’t travel home. Others are looking to us as a potential solution—you’ve found your business unexpectedly disrupted and are wondering if Slack is a safe and reliable way to reconnect and move forward. For those of you already using Slack, we are taking this opportunity to provide more visibility and clarity into Slack’s business continuity strategy so you can be confident that we will be available throughout this disruption. And, for those of you not yet using Slack, we wanted to provide some information about our free product offering, some general information on security and reliability, and resources to learn more.

There are two themes in the questions we’ve received: can Slack’s business continue to run, and can Slack’s infrastructure scale to handle additional load. We will address both in detail below. The short version is this: we are executing against our pre-established business continuity and pandemic plans, and we are confident in our product’s technical architecture and its ability to handle increased volume and load. Our employees are safe and are able to continue working as normal—wherever they are.

Keeping our business running

Slack has had a business continuity plan in place for years. It is regularly reviewed and updated, both on a periodic cadence and as needed to address significant changes. Recognizing the criticality of our own business in the event of a pandemic, we also had a pandemic-specific playbook prepared. We are using both of these plans in tandem now.

The business continuity plan came into play specifically due to the potential exposure in our San Francisco headquarters—this plan outlines steps we must take in the event of a headquarters-impacting event. Our office will be thoroughly cleaned over the weekend and is expected to be back in operation by Monday, but our work has not paused at all, even as we moved to remote operations.

The Slack you know today—both the product and company—would not exist without remote work. Our original team had two fully remote employees; the rest of the team was split between two offices in two different countries. This created a style of work that is deeply embedded in our culture, and it is one that ensures that being separated from our teammates does not impact our ability to do our jobs.

No matter what kind of work we’re doing, we use Slack to do it. All of our work happens in channels—this is where questions are asked and answered, where decisions are made and preserved, where documents are shared and collaborated upon, and where status is tracked and updated. Thus, being away from the office is of little consequence to how we actually work; beyond spending more time in videoconferences, little is different today from how work normally gets done.

Keeping our product running

Slack is a global business. On any given day, more than 50% of our users are located outside the United States. Our system architecture is designed to automatically accommodate the surges of traffic throughout the day that this brings to our systems, ensuring that our server capacity matches not only the demands being placed on the system, but also the region from which that demand is originating.

Our architecture is also highly distributed. Slack is deployed in different AWS data centers around the world to ensure redundancy in the event that one region becomes unhealthy or goes offline entirely. We regularly simulate and test these failure scenarios by simply taking an entire region offline and ensuring that traffic flows to the next, closest region—we would expect a simulated failure in London, for example, to seamlessly transition to Dublin and Paris. As part of doing this, we ensure that the regions capturing the unexpected excess traffic automatically scale up to meet the new demands.

While no systems can perfectly anticipate every contingency, we watch our systems scale up and down in real time every single day. Because of this, and because we conduct these additional disaster testing scenarios several times per year, we’re confident that the same architecture will scale up to handle any additional demands placed on the system due to heavier general use. Additionally, the demands on our infrastructure do not change when employees shift away from working together in the same office; there is no difference in load on our systems whether people are connecting from their office, a cellular network, or their home. Employees are already logged in for an average of nine hours per day; in other words, we are already handling high volume.

If your business is not already on Slack

We offer a free plan with no strings attached—no credit card required and no obligation to pay. It is a robust offering that will help your team continue working through this pandemic.

Every customer, whether paid or not, receives the same level of enterprise-grade security. You can read more about our security program and ensure that our certifications and attestations cover your business needs at

Slack is a critical business tool to millions, and we commit to a commensurate level of availability and reliability. We hold ourselves to a 99.99% Service Level Agreement—no more than 4.3 minutes of downtime per month. Our aggregated availability over the last six months is 99.998%.

Getting started on any new tool can be hard, especially under difficult circumstances. And we want to help, so we are offering a variety of resources to help you get going on Slack right away as part of your own management of this crisis. Contact us to set up a 20-minute call to help you get started. We’re also offering a series of webinars specifically on remote work where we’ll happily take your questions; sign up for a session here. Finally, we have a section dedicated to remote work in our Resources Library, where you’ll find both useful tips for the short term and ways to think about your strategy for the long term.

For further details about scale and our infrastructure, see our SEC filings.

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