nearmap.com C# Test

Welcome to the nearmap.com C# test. The purpose of this assignment is to test your familiarity with C#, distributed systems concepts, performance benchmarking and TDD.

Background

The source code that you are given is a very simple imitation of a key/value store:

• DatabaseStore is the central store that takes a while (500ms) to store and retrieve data.
• DistributedCacheStore is an interface to a distributed cache that takes much less time to turn around (100ms to store or retrieve).

This scenario is a simplified example of a typical high performance server cluster with a database, a distributed cache and multiple worker nodes.

Assumptions

After startup:

• Data in DatabaseStore never changes and can be cached forever.
• If DatabaseStore.GetValue() returns null for a key, the requested data item does not exist and will never exist.
• DistributedCacheStore is initially empty.

Task

Complete the 2 parts below & submit the solution. If the solution is incomplete, please state what hasn't been finished and outline how you are planning on solving it.

• Unless otherwise stated, the provided code can be modified at will
• The whole solution must build with no errors.
• You can use Visual Studio or any other C# IDE.

Part 1

Implement the IDataSource interface to create a mechanism to retrieve data from DatabaseStore with lowest possible latency. For a frequently-requested item your IDataSource.GetValue() implementation should have a better response time than the distributed cache store (ie < 100ms).

• The user of the IDataSource interface must not have to deal with thread synchronisation.
• You must write unit tests for all new functionality, and all tests must pass.
• You can use any publicly available libraries in unit tests
• Your non-test code can use an IoC library if desired, and otherwise only .NET Framework or .NET Core libraries/classes

Part 2

Complete the Main() to test your IDataSource implementation; it must:

• Populate DatabaseStore with the following data at startup:

    | key          | value         |
    --------------------------------
    | key0         | value0        |
    | key1         | value1        |
    | key2         | value2        |
    | key3         | value3        |
    | key4         | value4        |
    | key5         | value5        |
    | key6         | value6        |
    | key7         | value7        |
    | key8         | value8        |
    | key9         | value9        |

• Use 10 threads, each making 50 consecutive requests for a random key in the range (key0-key9). I.e. there would a total of 500 requests.
• For each request, print the managed ThreadId, requested key name, returned value, time to complete that request; similar to the following example:

    [1] Request 'key1', response 'value1', time: 50.05 ms
    [2] Request 'key2', response 'value2', time: 50.05 ms

Submission instructions

• DO NOT fork this repository or create pull requests on it, because we don't want other candidates to see your solution.
• Provide your solution as a .zip or .gz archive file, either via email or some Dropbox-like service, to your Nearmap contact.