Focus points:

• Ruby and gems administration with rvm
• Database Sqlite3
• Only one route, only one controller
• One ActiveRecord Model (CryptoCoin), One PORO (InvestmentCalculation)
• Singleton emulation on CryptoCoin for eth and btc price persistance.
• Added a app/services for API request and investment calculation processing.
• CoinMarketCap API usage
• SyncCoinPriceService for remote and local syncing, prevents more than one request per-minute to the remote server.
• InvestmentCalculationService for monthly calculations using ruby
• HomeController with html and js view rendering
• Added only 2 gems to the raw project:
  • Figaro for environment administration
  • Httparty as a client for the API requests

Missing:

• No testing
• CSV/JSON download ( serialization or send_data with mime-type would have done the trick )
• Show on realtime coin prices ( ajax polling, wss doesn't fit )