Your team is working on a video hosting website, similar to the likes of YouTube, Dailymotion, and so on, that has grown over time. The website had hundreds of videos and registered users earlier, but now has millions of videos and users. Due to its exponential growth, some of the solutions used for the problems of the past are the cause of the websites's problems today. To solve these problems, the founders of the website have hired your team. One of the issues is with the login system of the website, which uses an email address as the login id and a password. Although the website is available publicly, users are urged to register on the website so that they can use the extra features. With the growth in the number of registered users, login authentication has starts to take more time. It has been discovered that most members are willing registering on the website, but they do not want to wait for the login process. 

To overcome this problem, the founders need a faster data structure in terms of finding the password for the given login id. You are also required to develop an algorithm that can find the member most similar to the logged-in member based on the videos watched by both of them. The company plans to use this data to offer video suggestions to the logged-in member. 

Programming language: Java and/or Python