design · 2026-08-01
How WhichBacklink Is Built: Design, Tech, and the Self-Hostable Trade-off
A backlink manager that runs on free-tier Cloudflare Workers + D1, with an optional AI agent for directory automation. Why we chose self-hostable over SaaS.
Most backlink tools are either expensive SaaS (Ahrefs, Semrush — $99–$139/month) or a free spreadsheet. WhichBacklink is a third option: a real manager that runs on free-tier infrastructure, owns its data, and is self-hostable. Here is how it is built and why.
The architecture
The app is a Next.js 15 App Router site compiled to a single Cloudflare Worker via OpenNext, with a D1 (SQLite) database binding. The public landing lives at /, the gated manager at /app/*, and the runner contract at /api/runner/*. A separate Cron Worker dispatches jobs every five minutes. The browser automation (an AI agent driving a real, headed browser for directory submissions) runs in a Docker container on a VPS, because Workers cannot run a browser.
Why two layers
Cloudflare Workers cannot run a headed browser, a mail client, or a multi-step agent loop. So the Worker owns data, UI, and scheduling, and a containerized runner owns execution. The split keeps the always-on part free (Workers free tier) and isolates the heavy, risky part (browser automation) where it belongs — on a machine you control.
The self-hostable trade-off
Self-hosting means you own the data (it is in your D1, on your account) and you are not locked into a monthly seat license. The trade-off is you deploy it yourself. We made that cheap and reversible: the whole thing runs on Cloudflare's free tier, and the runner is a single Docker image you can move between VPSes with docker compose down on one and up on another.