System design : design an appstore like google playstore

First of all we need to figure out the features that we need for our appstore. Lets list them one by one.

- Login
- User page
   - Basic details
   - Mobile OS
- view already submitted apps
- apps detail page
- Install feature 
   - Check for the compatility of OS
   - Download
- Publisher page
   - Upload feature
   - Permission required
   - How do we store these binaries ?
- App search
- Roll out updates

Ok ! we are almost done with the requirements. Main points to be taken care for this application should be ..

- How do we upload files ? What are the different protocols ?

Lets go in detail and find out how does the file transfer works internally. Main protocols that are used for file transfer are,

FTP - FTPS(secure) &  HTTP - HTTPS(secure) 

SSL is used to secure the protocols for file transfer where it will encrypt the contents before sending. 

Understanding the basics

If you want to dive deep into the actual implementation of the FTP or HTTP , then we need to start from the basic OSI layers. Different layers of the OSI work together to transmit data from one host to another remote host.

Good understanding and explanation of the OSI layers can be found here. Basic network concepts and terminologies are found out here as well. TC/IP details can be found out in this link.

Read more about how FTP works here.

The question was whether we should use FTP or http. ftp is a clear winner in case of transfer speed, but properly tuned http can counter that by parallel processing of chunks. ftp's security i still a concern as most of the firewalls will stop it. nowadays ftps are becoming obsolete. the large file transfers can be done with http. So n network application http is a better option for large file transfer.Since our use case of app binary files will be smaller in size , we will sure surely use http based file transferring.

Some of the techniques that can be used for transferring large files are chunking, file streams etc. Here is a good article on large file transfer over http.

- How does we store all the binary files ?

We can store these files in a file server for mostly active files and web can move it storage servers once it having less activities.

File server is used for sharing/distributing large-sized files amongst a large group of users across multiple locations. These have high-speed connectivity & high amount of bandwidth.

File storage server is used to host synced or backed-up files from PCs and smartphones. These are not used to share files and typically have large amount of storage and low-to medium speed connectivity with high bandwidth.

- Make it highly available




API design
Data modelling