They had a really smooth process. The first was an Online Assessment. Not hard at all, and not the typical IQ test. They said they focused more on the readability and implementation rather than the algorithmic thinking. The question was clear and you did not even have to come up with the algorithm. The question also focused more on your DS knowledge. If you know how the typical DS work, you will definitely ace it.
Then you will have a brief conversation with the recruiter, and I would recommend knowing a bit about the company.

After that, there is an onsite. Two interviews: one on DSA and another on system design. The interviewers are so cool and kind, it felt more of a conversation than an interview. The DSA focused more on again on DS. It was kind of a variation of LRU. I think the most important thing here was seeing how you think and the conversation you have. Even though you might know how to do it, it is better to talk through different approaches and DS.

The system design was more focused on API and just an assessment of your experience with projects. If you have done at least one web app, you will ace it. Don't stress about the complicated stuff, that is for the seniors.

I mean... that's it. The whole process was amazing.
P.S. one thing I can also emphasize is that Squarespace focuses more on web apps so be sure to put at least one project on that.