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JUST EAT Test Data Engineer Recruitment Test

Thank you for taking the time to do our technical test. It consists of two parts:

In order to avoid bounced emails we would like you to submit your results by uploading the relevant zip file to a shared Google Drive folder. In order to obtain the URL for this folder please supply your Gmail or Google-based email address to either your agent or the JUST EAT member of staff who assigned you the test.

Please make this a single zip file named {yourname}-{role-applied-for}.zip containing:

  1. a single markdown file with the answers to the technical questions
  2. one folder containing the technical test

Technical Test

JUST EAT raises a variety of events but the core business events consist of OrderPlaced, OrderAccepted and OrderCancelled.

The technical test consists of two tasks:

  • Write an app that can generate core business events in batches; then write those events to a JSON delimited file at specified intervals.
  • Stream the JSON delimited files that you generated in step one into program which will output a running count of each event type to the terminal every five seconds.

  1. Write an app that can generate core business events:

    • Each order will produce two events namely (OrderPlaced, OrderAccepted) or (OrderPlaced, OrderCancelled).

    • For every five orders, four orders will consist of OrderPlaced and OrderAccepted events and one order of OrderPlaced and OrderCancelled events.

    • The batch of events within a given interval should be stored in a JSON delimited file named orders-<timestamp>.json ex. orders-2017-05-14-18-47-29-879763.json

    • The app must take 4 arguments

      • number-of-orders - Number of orders to generate which will each produce two events.
      • batch-size - Batch size of events per file.
      • interval - Interval in seconds between each file being created.
      • output-directory - Output directory for all created files.

    • How to run the app

       generate-events --number-of-orders=1000000 --batch-size=5000 --interval=1 --output-directory=<local-dir>

    • Example shows a snippet of ten events from the content of a generated file. Each event is on its own line separated by a linebreak.

       { "Type": "OrderPlaced", "Data": { "OrderId": "3cb0f939-9398-4d29-a28f-2a1a3a6ce3b2", "TimestampUtc": "2017-05-14T19:12:32Z" } }
 { "Type": "OrderAccepted", "Data": { "OrderId": "3cb0f939-9398-4d29-a28f-2a1a3a6ce3b2", "TimestampUtc": "2017-05-14T19:12:32Z"} }
 { "Type": "OrderPlaced", "Data": { "OrderId": "a7d86ca5-7541-4c86-a7ad-1bec2b070b3c", "TimestampUtc": "2017-05-14T19:12:33Z" } }
 { "Type": "OrderAccepted", "Data": {"OrderId": "a7d86ca5-7541-4c86-a7ad-1bec2b070b3c", "TimestampUtc": "2017-05-14T19:12:33Z"} }
 { "Type": "OrderPlaced", "Data": { "OrderId": "757001d9-a454-40d3-a14b-9f0f9440be9f", "TimestampUtc": "2017-05-14T19:12:34Z" } }
 { "Type": "OrderAccepted", "Data": { "OrderId": "757001d9-a454-40d3-a14b-9f0f9440be9f", "TimestampUtc": "2017-05-14T19:12:34Z"} }
 { "Type": "OrderPlaced", "Data": { "OrderId": "4f3fd16c-4685-45e6-a6f9-823f5f73a7d0", "TimestampUtc": "2017-05-14T19:12:35Z" } }
 { "Type": "OrderAccepted", "Data": {"OrderId": "4f3fd16c-4685-45e6-a6f9-823f5f73a7d0", "TimestampUtc": "2017-05-14T19:12:35Z"} }
 { "Type": "OrderPlaced", "Data": { "OrderId": "812a8469-68d0-4c9b-8429-d46d51d63db3", "TimestampUtc": "2017-05-14T19:12:36Z" } }
 { "Type": "OrderAccepted", "Data": { "OrderId": "812a8469-68d0-4c9b-8429-d46d51d63db3", "TimestampUtc": "2017-05-14T19:12:36Z"} }
 { "Type": "OrderPlaced", "Data": { "OrderId": "8825cd95-f172-4132-9793-864b4dd725df", "TimestampUtc": "2017-05-14T19:12:37Z" } }
 { "Type": "OrderCancelled", "Data": {"OrderId": "8825cd95-f172-4132-9793-864b4dd725df", "TimestampUtc": "2017-05-14T19:12:37Z"} }

    • Every OrderPlaced event must have a OrderAccepted or OrderCancelled event with the same OrderId.

  2. Write a streaming app:

    • Monitor a given directory for new files.

    • Process new files containing order events.

    • Output a running count for each event type to the terminal.

    • Keep a 5 second delay between each terminal output.

      ex. Terminal displaying a running count of each event type from the previous JSON snippet

       "OrderCancelled": 1
 "OrderAccepted": 4
 "OrderPlaced": 5

Platform Choice

You can create the solution in any language or framework of your choice.

Task requirements

Feel free to spend as much or as little time on the exercise as you like, as long as the following requirements have been met:

  • Please complete atleast one of the tasks decribed above.
  • You should provide clear instructions on your test setup and how to execute your tests. The clarity and precision of these instructions - and the ease with which the interviewers can execute them - will be a key part of the assessment. Please create a README file detailing said instructions. Please also use this file for listing any additional comments or observations you might want to share about your submission.

Technical questions

Please answer the following questions in a markdown file called Answers to technical questions.md.

  1. How long did you spend on the coding test? What would you add to your solution if you had more time? If you didn't spend much time on the coding test then use this as an opportunity to explain what you would add.
  2. Why did you choose the language you used for the coding test?
  3. What was the most useful feature that was added to the latest version of your chosen language?
  4. How would you track down a performance issue in production? Have you ever had to do this?
  5. Please describe yourself using JSON.

####Thanks for your time, we look forward to hearing from you!