Their interview process is well documented (for instance, here https://clevercoder.net/2017/09/04/toptal-passed-interview/). My experience was that it was doable, though you need to brush up your algorithm skills and have luck with the problems you get.
The interview process is onerous more than difficult: mostly leetcode style questions that need lots of practice for, plus a basic but time-consuming take-home task.
And for me the scheduling was super difficult: the whole process took weeks, with the only times available at odd hours West Coast US time, and my recruiter flaking and rescheduling once.
Beyond some basic level of coding, it's more a test of patience and time.
Automatically evaluated leet coding session (2 hours) + Live English language check interview (15 mins) + 2 week fake template project + Live coding session (30 mins).
I was fortunate enough to pass everything without additional attempts and had no job at that time. Some of my friends got in after 1 year (after you fail at some step, 2nd attempt is delayed), some never managed to complete the whole process.