Shipping the Salesforce Day One Campaign
When Salesforce closed its $27.7 billion acquisition of Slack on July 21, 2021, it marked the culmination of months of behind-the-scenes work across both companies. For the frontend engineers on Slack's Customer Acquisition team, that meant rolling out a coordinated set of web updates under tight deadlines, with dozens of stakeholders and no room for error.
The Customer Acquisition team owns Slack's web properties, with a mission focused on top-of-funnel growth: driving awareness, generating interest, and increasing the number of new Slack teams created each week. That puts the team in an unusual position within the engineering organization—while it sits under Engineering, its primary stakeholder is Marketing. The result is a fast-paced environment where project priorities can shift quickly, and where work has immediate, measurable impact across the more than 400,000 users who visit slack.com daily.
A Stack Built on Hack
Despite appearing modern and dynamic, slack.com does not rely on React or Vue. The team uses Hack, a typed language based on PHP that Facebook developed in 2014, to generate HTML, with JavaScript and LESS layered on for interactivity. That means the primary technical challenge for the acquisition campaign was simply learning to work in a new language.
The rollout itself had two main deliverables: a new landing page and a series of copy and layout changes across multiple slack.com pages. One notable change requiring legal approval was replacing every instance of "Slack Technologies, Inc." with "Slack Technologies, LLC, a Salesforce company." Even this seemingly straightforward edit touched both internally- and externally-owned web properties and required full translation across all supported languages—turning small tasks into mid-sized projects.
The team builds on Spacesuit, its internal web design system, which provides reusable components that made constructing the new landing page straightforward. The project scaffold was ready nearly a month before the launch date, but the weeks leading up to rollout involved merging multiple pull requests daily to incorporate design updates, bug fixes, and copy changes from the many teams involved—including Design, Copy, Quality Engineering, and Localization, as well as Slack's executive leadership and Salesforce counterparts.
Coordinating Launch Day
Deploying changes across the site was handled through Houston, Slack's internal product rollout system. Houston offers unified controls for running experiments like A/B tests and rolling out features via simple feature toggles. For this project, the team used a Houston toggle to push all website changes out simultaneously, timed to align with the broader run-of-show schedule that included the press release, blog post, and social media announcements.
Launch was scheduled for around 9 am ET on Wednesday, July 21, with the team required to be ready an hour earlier. The rollout went smoothly—almost anticlimactically so, one engineer noted—with only a single minor issue that was quickly identified and resolved after launch. The event itself had already been delayed from its initial estimate by about six days.
Lessons From a High-Stakes Rollout
The project came with rapidly changing requirements—the kind of "spicy" work that the team's manager liked to reference. With this being a high-visibility effort involving two large companies and more than 40 stakeholders, communication proved essential to success.
Several practices stood out as particularly valuable: posting engineering updates to the project channel at least every other day so the whole team stays informed, and asking questions publicly in channels rather than in private messages. This helps keep knowledge and history accessible to everyone involved.
Beyond the Campaign
Work continued after the acquisition announcement. In subsequent weeks, the team focused on performance improvements across slack.com, including adding browser-level lazy loading for images, minimizing Content Layout Shift, and improving Largest Contentful Paint. These efforts brought LCP under 2.5 seconds on desktop for more than 2,300 pages. The team also updated and created new reusable components in Spacesuit and customized the WordPress CMS system that feeds data to many pages across slack.com in preparation for Slack's annual Frontiers conference.
For an intern coming in expecting to work on the Slack app itself, the experience of shipping web pages during one of the largest tech mergers in history proved to be exactly the kind of cross-functional, high-impact work that makes a summer internship memorable.
