Create a To-Do list API where the tasks and all their history of changes are stored on a Blockchain.

Your childhood friend, Clay, is the biggest fan of all things related to the Blockchain technology. You've been listening to him for months and years talking non-stop about cryptocurrencies and the security of decentralized data storage.

Despite Clay's insistence on you investing in cryptos, the truth is that what you've always been interested in how the Blockchain can be applied in other applications beyond cryptocurrencies.

So, as a software developer, you decide to create your own project with this technology: a to-do list app that stores all the tasks and their history of changes in Blockchain.

Ideal for

Junior developers

Available stacks

Java · Python · TypeScript · JavaScript

Required experience

Basic knowledge


This API has to allow the user to add new notes and mark them as completed. The flow will be always the same: first you need to add a new note/task and then you save it on the Blockchain. In order to make the Blockchain data persistent, we need to store the Blockchain in a file.

You could find the API description on the OpenAPI description file.


  • Send request to the API to add or mark as completed any task
  • Load the Blockchain data from the file, if exists
  • Create a Block with the new to-do/task data
  • Add the new Block to the Blockchain
  • Save the Blockchain with the new data on a file
  • Solve the challenge and show your potential
  • Defend your solution by explaining your code.
  • Get feedback on your code from experts.
  • Build your technical portfolio with all your completed challenge 
  • Create an app and test your coding skills
  • Feedback from our expert Tech Mentors
  • A complete report of your skills - with the possibility of sharing it
  • Your own technical portfolio to use in job interviews


Mauro Gómez

Mauro Gómez is the CTO and Co-Founder of Rviewer. Software Engineer with more than 7 years of experience both as a developer and as a researcher in the field.

He has done research in prominent places such as the Barcelona Supercomputing Center, and worked in leading companies such as Adsmurai, as Team Lead and Big Data Developer, or Sabentis, evolving its SaaS platform.

Start now this PrivaTo-Do challenge

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