Kalsofit
A personalized fitness platform — ~50 SEO calculators plus a SaaS app with AI coaching, tracking, and billing in one server-rendered codebase.
Kalsofit is a health and fitness platform that pairs a public, SEO-first content site (~50 calculators, blog, resources) with an authenticated SaaS app (dashboard, tracking, AI coach, notifications, billing, admin).
Both experiences ship as a single server-rendered Astro 7 application with Svelte 5 islands on Neon Postgres via Drizzle ORM, deployed to Vercel by default or Railway as a container. The full engineering report — request lifecycle, data model, AI gateway, billing, security posture — is published in the architecture handbook.
Architecture &
Build Process
Key Architecture Decisions
One Astro SSR monolith
Site and SaaS ship as a single server-rendered app with Svelte islands instead of separate services.
Dual deploy target
Vercel and Railway builds come from one config via DEPLOY_TARGET.
ISR with exclusion list
Public pages cache at the edge; every personalised route is explicitly excluded.
Entitlements over roles
Feature access is gated by plan entitlements, never user.role.
Multi-provider AI Gateway
In-house gateway fronts five LLM providers with failover; each activates only when its key is set.