Directly after call I got hometask which is asks to implement - unique 7 character alphanumeric human readable ID(AB12CD9). There are another branches where you can test your solution against those tests.
Sigiloso
My final solution passed all tests but it made company to response me instantly that they are not look for this solution. After long discussion with reviewer/technical manager he mentioned that they expect some low level solution and the test are not metric that your code is good enough. And you need to write production ready code, for example if it breaks then after that it must start from the last iteration. But this requirement didn't asked during task requirement or with test cases.