Leg 04 / Own product / 2026
Signlyo, a SaaS shipped solo
HTML email signatures and digital business cards, freemium. Designed, built, made compliant and launched on my own. Published by my company, Axion Development.
Visit signlyo.comFlight plan
- Period
- April to September 2026
- Role
- Founder, sole developer
- Team
- Solo project
- Stack
- React 19, Vite, Convex, Coolify
- 1
- person for product, code, compliance and launch
- 4.5 months
- from first commit to launch
- 0
- manual steps between sign-up and subscription
A user's journey
From creating a signature to subscribing, with no manual step.
- WP01EditorSignature and card, 4 themes
- WP02CopyGmail-compatible rich text or raw HTML
- WP03Public cardQR code, vCard, offline PWA
- WP04SubscriptionPayment, plan limits, lifecycle emails
The product
Email signatures that work in the main mail clients, with an installation guide for each, and digital business cards shared by link or QR code. The free plan shows “Made with Signlyo”, which turns every email sent into an acquisition channel.
What I did
- The full product: editor, analytics with daily rollups, feature flags, back office, French and English.
- Authentication with Better Auth and two-factor authentication.
- Payments with LemonSqueezy, which handles VAT as Merchant of Record.
- Commercial compliance: terms of service, legal notices, consent to waive the right of withdrawal.
- Deployment: front end on Coolify, back end on Convex, GitHub Actions CI with type checks, tests and lint.
One decision
Plan limits enforced on the server
- Context
- The free plan includes one signature and one card; a limit checked only in the UI can be bypassed with a direct call.
- Decision
- Limits are checked in Convex mutations, and the subscription is synced through an HMAC-signed webhook.
- Consequence
- A free account cannot exceed its quota, even by calling the API directly.