Revolut Backend Test

Tech Choices Notes

1. Programming language used is Java version 11
2. Gradle is used as the build system
3. Libraries used as as follow
   • JavaSpark - Framework for REST
   • Guice - Dependency Injection
   • Hibernate - ORM
   • H2 - Database
   • Junit 5 & Mockito - For testing and mocking

Implementation Notes

1. This is a single gradle module project. This has been done to keep navigating through the project simple. Ideally I would like to break the project down into multiple gradle modules which can depend on each other and can build and run independently.
2. The solution implemented assumes that the account can have just a Single Currency stored in the account table. Extension is possible in future.
3. Some of the Implemented database queries (like get all transactions) are not optimised for HUGE amounts of data. This can be improved in future.
4. The solution has 3 different Resources
   • Account - To create & retrieve accounts.
   • Transfer - To initiate a transfer between 2 accounts.
   • Transaction - To view all transactions and their states for a given account.

How to run

1. Build
   • Linux - ./gradlew clean build
   • Windows - gradlew.bat clean build
2. Run (Default port used is 8000)
   • Linux - ./gradlew clean run
   • Windows - gradlew.bat clean run

Endpoints

Once the server is running use the following end points to interact with the server.

1. Accounts

   • Get account by id - GET - localhost:8000/api/account/{accountId}
   • Create an account - POST - localhost:8000/api/account/ with body

   {
      "balance": 1
   }
   

   Response

   {
     "id": 1,        
     "balance":  1
   }

2. Transfers

   • Transfer money POST - localhost:8000/api/account/ with body

   {
     "senderId": 1,
     "receiverId": 2,
     "amountToTransfer": 0.5
   }

   This returns an OK response when transfer gets queued. The transfer can be executed anytime in the future. It is not synchronous. This has been done to allow the transfer model to work across multiple servers if needed. For the current implementation, it just runs the transfer on the same thread. This can be easily changed by updating the executor type in TransactionModule.

3. Transactions

   • Get all the transactions for account id GET - localhost:8000/transactions/{accountId}

   Response

   [
      {
          "transactionId": 1,
          "senderId": 1,
          "receiverId": 2,
          "amountToTransfer": 0.50,
          "transactionState": "SUCCEEDED"
      },
      {
          "transactionId": 2,
          "senderId": 1,
          "receiverId": 2,
          "amountToTransfer": 0.50,
          "transactionState": "SUCCEEDED"
      }
   ]

Tests

1. Unit Tests

   • Linux - ./gradlew clean test
   • Windows - gradlew.bat clean test

2. Integration Tests

   • Linux - ./gradlew clean iT
   • Windows - gradlew.bat clean iT