How Klaviyo shipped 356 internal apps in two weeks on Vercel
Klaviyo on Vercel
Built a platform for shipping internal apps
512 builders and 356 live apps in two weeks
Every app ships SSO-gated and private by default
Builders go from idea to live app in 3 minutes
Klaviyo is a B2C CRM for more than 200,000 brands. It brings marketing, service, agents, and data together in one platform so brands can deliver customer experiences at scale. Klaviyo built a platform on Vercel for shipping internal apps, then opened it to every employee through a citizen developer program.
In the first two weeks of the program, 512 of Klaviyo’s more than 2,000 employees deployed 356 apps on Vercel. Of those, 196 were full-stack apps with their own databases. The teams that are now shipping software include legal, marketing, and HR. "The next big thing at Klaviyo could be in a marketer's laptop," says Sr. Lead AI Architect Mohamed Ali.
Guardrails instead of walls
Opening deployment to a couple thousand new builders made security the first conversation. The obvious way to keep them safe is to broadly restrict what they can do. Klaviyo went the other way.
Employees aren't just building microsites; they are shipping full-stack apps on top of Klaviyo's own databases, and none of it touches the public network. Every builder is managed through Klaviyo's identity provider, which Vercel made possible through Enterprise Managed Users.
Implementing safeguards across the stack
Secure Compute gives Vercel deployments a private network path into Klaviyo's own infrastructure. Apps built in the program read from and write to Klaviyo's databases without any traffic crossing the public internet. That's what made bring-your-own-database work for Klaviyo.
On top of that connection, Vercel Passport and Klaviyo’s identity provider give every app the same access defaults, with nothing for the builder to configure:
Apps are private and SSO-gated through Okta
Sensitive environment variables are set at the team level, out of builders' hands
Klaviyo's hardened GitHub security is inherited by every project
Wiz scans every project, and findings feed Klaviyo's SIEM
Public deployment is granted case-by-case, so sales can share microsites with prospects, while internal tools stay private
How Klaviyo's app platform turns an idea into an app
Klaviyo wanted anyone with an idea to be able to describe it in plain language, from Slack, Claude, or Cursor, and get back a working app. They designed K:Forge, an in-house pipeline built on the Vercel SDK, to handle everything in between.
K:Forge creates a GitHub repo, deploys the app on Vercel, connects data through Secure Compute, and applies every security default. The output is a live, SSO-gated app, and the builder never touches infrastructure. Changes work the same way: mid-thread in Slack, someone can tell K:Forge what should be different, then it makes the change and redeploys.
Klaviyo built the pipeline and deliberately didn't build the layer under it. CDN behavior, preview environments, analytics, global scale: all of it is R&D Vercel had already done, so builders and engineers at Klaviyo don't have to think about it.
For bigger builds, citizen developers take an app about 80% of the way, and Klaviyo's platform team steps in for the last 20%, for fine-tuning and safety review. The platform team went from being the bottleneck to being the finishing touch. "We don't worry about scale," Mohamed says. "If 100,000 people hit an app, Vercel already solved that."
What people at Klaviyo are building
Employees build everything from microsites that rework a sales process to full-stack apps for problems too niche for any vendor tool. For K:BOS, Klaviyo's flagship event, the team skipped off-the-shelf registration tooling and built its own. Engineering barely touched it.
Klaviyo was one of the first customers of Vercel for Enterprise Apps and Agents. The platform gave the company a way to let anyone build full-stack apps, with security handled by default.
What's next
Klaviyo sets a high bar for AI fluency. One in five employees has shipped an app so far, and Mohamed intends to get even more people building. The team is also going deeper into Vercel, with MCP and AI Gateway.
About Klaviyo: Klaviyo is an autonomous B2C CRM that powers more valuable customer experiences. We unify a flexible, scalable data platform, intelligence that gets smarter with every interaction, and action across Marketing and Service to help businesses turn real-time customer data into personalization at scale.