Following a couple of general introductory interviews (over Skype), came a deep technical assessment in the form of a technical online test.
The test took ~2½ hours (each question is time limited) and was comprised of questions and short tasks, some in the form of multiple choice, and some were open questions.
As the Tech Lead position is for highly experienced professionals, the assessment was quite elaborate, spanning topics like (partial list): HTML 5, CSS 3, JavaScript, network protocols, object oriented software design, architectural patterns, code analysis, technological literacy, logic, a few progressive matrices of shapes and numbers, and (unrelated) general knowledge.
The assessment was a bit stressful, as it was covering so much, in limited time, but it was followed a few days later, by another Skype call, in which each question and answer were reviewed and discussed in depth.
In my opinion, this review step, was very helpful, both for me (as I was given a chance to explain myself, defend my answers, even ones I didn't have much time to articulate in great detail in real time), as well as for the company (which could assess my attitude, and see how much I really know, or weather I was just guessing or cheating). This step gave me clarity, and made me feel better about the entire assessment step.
Following this, I was invited to the Emakina office in Amsterdam, for a face-to-face interview with the head of development, and one of the managing directors. That interview was also with good spirit and mutual interest. It also gave me a chance to meet some of the people, and get an impression of the office (which is awesome, by the way).