How Klaviyo shipped 356 internal apps in two weeks on Vercel
Klaviyo enabled over 500 employees to deploy 356 internal apps in two weeks using Vercel’s platform, including 196 full-stack applications with private database access.
Klaviyo, a B2C CRM platform serving over 200,000 brands, built an internal development platform on Vercel to allow employees to create applications without traditional engineering bottlenecks. Within two weeks of launching a citizen developer program, 512 of Klaviyo’s more than 2,000 employees deployed 356 apps, including 196 full-stack applications with dedicated databases. Teams across legal, marketing, and HR participated, demonstrating the platform’s broad accessibility. Klaviyo’s Senior Lead AI Architect Mohamed Ali noted that the initiative could lead to innovative solutions emerging from unexpected teams.
Security was a primary concern as Klaviyo expanded deployment access to thousands of new builders. Instead of imposing restrictive controls, the company leveraged Vercel’s Enterprise Managed Users and Secure Compute to provide private network access to Klaviyo’s infrastructure. Apps built through the program interact with Klaviyo’s databases without exposing traffic to the public internet, enabling secure full-stack development. Vercel Passport and Klaviyo’s identity provider ensured consistent access defaults, eliminating manual configuration for builders.
To streamline app creation, Klaviyo developed K:Forge, an in-house pipeline built on the Vercel SDK. K:Forge automates the entire process, from creating GitHub repositories to deploying apps on Vercel, connecting data via Secure Compute, and applying security defaults. The result is a live, SSO-gated application that builders can modify mid-thread in tools like Slack, with changes automatically redeployed. Klaviyo deliberately avoided rebuilding underlying infrastructure, relying instead on Vercel’s existing capabilities for CDN behavior, preview environments, analytics, and global scale.
The platform team at Klaviyo shifted from being a bottleneck to providing final touches, handling fine-tuning and safety reviews for larger builds. Employees have created diverse applications, from microsites optimizing sales processes to full-stack tools addressing niche needs. For Klaviyo’s flagship event, K:BOS, the team built a custom registration system without relying on third-party tools, with minimal engineering involvement. Klaviyo continues to expand its use of Vercel, including integrating MCP and AI Gateway.