Recruiter reached me in LinkedIn. He described an opportunity in Thesys to me, was very positive and supportive. Interview process starts with HackerRank test. I had two hours to solve 5 tasks, including "hard"-ranked ones. Due to the nature of HackerRank tasks, you must be very well traineed on that platform to (a) rocket-jump thru boilerplate code (b) and avoid long integer traps (c) for hard tasks, foresee bottlenecks from input data limitations. - Train on string parsing/formatting - just typing deserialization code for your custom struct/data from a platform-provided string might take a lot of time. - Pay attention to integer sizes; in many tasks you should use 64 bit ints to pass. - Design better solution on paper, if the first one has O(N^2) complexity on 1 < N < 1E9, before start to code. Refresh you knowledge on standard algorithms and data structures, including algorithms on strings, graphs, balanced trees. I failed Hacker Rank test but Thesys gave me a second attempt. It is similar to a first HackerRank test, so I get bored and gave up after 30 mins. Anyway I'm impresed by Thesys's will to hire people. I had an impression they are looking for a fast-typing dual-wield programmer for a big money. A couple month of daily trainig at any coding platform would give you a great chance to succeed in the first interview phase. Call me dumb, but without appropriate training one of the suggested hard tasks took me 3.5 hours to solve offline and meet complexity criteria while you will have just 30 minutes to code it or so. I recommend not even try a test before you solved 50 moderate and 15 hard task on HackerRank first in a recent month. The well-trained criteria: you solve random hard task within 25 minutes. So, be trained and good luck!