Guardrails, not walls: the security model
Opening deployment to a couple thousand new builders made security the first conversation. The obvious move is to restrict what those builders can do. Klaviyo did the opposite, leaning on Vercel to engineer defaults rather than block access.
Employees aren't just building microsites. They ship 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 enabled via Enterprise Managed Users.
Safeguards applied across the stack
Secure Compute supplies a private network path from Vercel deployments into Klaviyo's own infrastructure, so apps in the program read from and write to Klaviyo databases without traffic crossing the public internet. That is what made bring-your-own-database viable.
On top of that connection, Vercel Passport and Klaviyo's identity provider give every app identical 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
K:Forge: plain language in, deployed app out
The goal was for anyone with an idea to describe it in plain language from Slack, Claude, or Cursor and get a working app back. Klaviyo built K:Forge, an in-house pipeline 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. What comes out is a live, SSO-gated app, and the builder never touches infrastructure. Revisions follow the same path: mid-thread in Slack, someone can tell K:Forge what should change, and it makes the change and redeploys.
Klaviyo built the pipeline and deliberately left the layer beneath it to Vercel. CDN behavior, preview environments, analytics, global scale — all of it was R&D Vercel had already done, so builders and engineers at Klaviyo don't have to think about it.
Bigger builds follow a handoff pattern: citizen developers take an app roughly 80% of the way, then Klaviyo's platform team handles the last 20% with fine-tuning and safety review. The platform team moved from bottleneck to finishing touch, and scale isn't a concern — if 100,000 people hit an app, Vercel already solved that.
Scale of the rollout
Klaviyo, a B2C CRM for more than 200,000 brands, first built a platform on Vercel for internal apps, then opened it to all employees through a citizen developer program. In the program's first two weeks, 512 of Klaviyo's more than 2,000 employees deployed 356 apps on Vercel, 196 of them full-stack apps with their own databases. Legal, marketing, and HR are among the teams now shipping software.
Adoption and what's coming
Employees cover a wide range: microsites that rework a sales process, and 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, with engineering barely involved. Klaviyo was among the first customers of Vercel for Enterprise Apps and Agents, which gave it a way to let anyone build full-stack apps with security handled by default.
Klaviyo sets a high bar for AI fluency. One in five employees has shipped an app so far, and the team plans to get more people building while going deeper into Vercel with MCP and AI Gateway. As Mohamed Ali, Sr. Lead AI Architect, puts it, there's no playbook for what a citizen developer program should look like, which makes a partner who can guide them through it important.
