We were discussing  SDK and command line interface CLI options in addition to the APIs which improve the customer base. Tests and automations can make use of commands and scripts to drive the service. This is a very powerful technique for administrators as well as for day to day usage by end users. Command line usage has one additional benefit - it can be used for troubleshooting and diagnostics. While SDKs provide an additional layer and are hosted on the client side, command line interface may be available on the server side and provide fewer variables to go wrong. With detailed logging and request-response capture CLI and SDK help ease the calls made to the services. 

Let us now consider applying the SDK and CLI to something that Is inherently UI specific – say the login page. The login page has a few more restrictions that other user interface probably don't have. First, it is central to the company where the login happens. People login because they trust the page they are on. This means the login page is inherently tied to the domain the web application hosted in. Even if a third party application wants to allow its user to login, it will redirect the users to login on the company page. Since a user interface is involved in specifying username and password, it might not seem likely to delegate it to a command line or sdk because that would involve sending the credentials in the clear. However transmitting the credentials can be done over encrypted channel as it is routed from one service to another. Besides we have never intended the user to provide the credentials anywhere other than the login page. The suggestion is merely to decouple the UI from being in the response body to being in a standalone web view that calls a service Since both the service and the UI need to available and hosted on the same domain, it doesn't matter whether the credentials get passed from the UI to the service via a form submit or via a relay from one service to another. The UI and service for the signin are merely shifting boundaries between the app and the service.  

Second users are accustomed to not disclosing their credentials. These work differently from key-value pairs. Many cloud providers use key-value pair in their SDKs and CLI. They know that their services such as compute and storage will be used in applications and services and therefore they find it easier to ship SDKs and CLIs. A user interface is a frontend only to a user and not an application or a digital asset. Therefore, providing an SDK or CLI does not hold as much appeal as a login page. At the same time, separating out the view for the user and focusing on the internal architecture with the help of SDK and CLI helps bring the best practice from the cloud to the retail. 

Lastly users are comforted knowing that they are signing in to a look and feel that they are familiar with. Therefore a login page is a frontend that users expect not to change. By the very same argument, if we pull the user interface out of the API response and let the UI be part of an MVC that makes internal service call under-neath, then we are less likely to make changes to the login page as the service gets revisioned. Moreover, the customizations that we need to make for third party, clients and end-users now don't need to run as deep as the service. 

#codingexercise

We were discussing finding closest numbers between the elements of three sorted integer arrays. 

Another usage of finding the closest numbers in these arrays to a given input value is to discover overlapping range of sorted numbers. In order to do this on number line, we could choose max(start1,start2,start3) and min(end1,end2,end3) for (start,end) pair for every array. And by finding the closest of the min and max values, we can determine the overlapping range projection on any one of three arrays. Then we can choose the projection with the smallest number of elements 

Determining the overlapping region projections helps shrink the search space for any operations involving any or all three arrays. It may not be useful for sum, average, mode or median but it is helpful for partitioning the number line to determine the presence of a number in any array. If the number is not in the overlapping range then we exclude one of the arrays and binary search for it outside the projections in other two arrays.

1. One such usage is goes back to determine the closest numbers of a given value. If the number is not included in the projections, we know that we can search in a smaller space