Castle vs Instant 2FA: What are the differences?
Developers describe Castle as "Track security events or any unstructured data from your web backend or mobile app, and Castle will look for anomalies". Castle looks for suspicious login patterns without bothering the legitimate user nor the site administrator. The fully-automated anti-hijack engine identifies potential account compromises based on where the user logs in from and how they navigate the site. On the other hand, Instant 2FA is detailed as "Add two-factor auth to any site in minutes". Add a powerful, simple and flexible 2FA verification view to your login flow, without making any DB changes and just 3 API calls.
Castle and Instant 2FA belong to "Security" category of the tech stack.