Replacing Calendly with Self-Hosted Easy!Appointments

Description and use

The author successfully replaced Calendly with Easy!Appointments, achieving cost savings and greater control. The decision was driven by UX quality and a manual code audit that revealed potential race condition vulnerabilities in both top candidates, highlighting the importance of auditing open-source code rather than relying on reputation.

Problem

The user wanted to replace Calendly to avoid monthly subscription costs, reduce third-party dependencies, maintain data privacy, and align with an Astro-based static site architecture that avoids heavy third-party scripts.

Outcome

The author successfully replaced Calendly with Easy!Appointments, achieving cost savings and greater control. The decision was driven by UX quality and a manual code audit that revealed potential race condition vulnerabilities in both top candidates, highlighting the importance of auditing open-source code rather than relying on reputation.

Workflow

• Identify self-hosted alternatives to Calendly (CloudMeet, Cal.diy, booking-calendar, Easy!Appointments).
• Filter candidates based on production maturity, UX quality, and framework compatibility.
• Discard CloudMeet and Cal.diy due to lack of track record and production readiness warnings.
• Compare booking-calendar and Easy!Appointments on UX and architecture.
• Select Easy!Appointments for its superior UX (monthly view, wizard flow) despite booking-calendar's cleaner backend architecture.
• Conduct a security audit of the selected tool's codebase, specifically looking for TOCTOU race conditions in slot booking.
• Verify that the booking logic correctly handles concurrent requests to prevent double-booking.
• Deploy the self-hosted solution.

Evidence

The catch: you're the product (nothing's really free), and your customer data lives somewhere you don't fully control and can't fully audit.

Source

Easy!Appointments won on UX. Onto the part that actually mattered for a production decision.

Source

Neither project is 'more robust' than the other on this specific point — both share the same design gap, independent of relative maturity.

Source