Backend Challenge

Your task is to create a backend for mini blockchain explorer. An example of a fully functional explorer can be found on https://explorer.energi.network/ for orientation.

Requirements

1. Use Golang or Nodejs
2. Create 2 (two) microservices
3. Raise an MR (merge request) so we can communicate
4. Any omitted details are omitted on purpose, use your best judgment to fill in the gaps

Structure

The two microservices should be:

1. Indexer (blockchain scanner)
2. Public facing REST API

Indexer

This backend service should scan for transactions and capture block information:

• number of transactions
• transaction details (hash, from, to, amount) Captured data should be inserted into the database of your choice.

CREATE TABLE blocks(
    number INT PRIMARY KEY,
    hash CHAR(32) NOT NULL,
    tx_count INT NOT NULL
);

CREATE TABLE transactions(
    block_number INT PRIMARY KEY,
    hash CHAR(32) NOT NULL,
    from CHAR(32) NOT NULL,
    to CHAR(32) NOT NULL,
    amount NUMERIC NOT NULL,
    nonce INT NOT NULL
);

The indexer should be able to scan the range if given from-to parameters, or simply subscribe to the latest blocks.

Examples:

• Indexer 100 200 should scan all blocks from 100 to 200 (inclusive)
• Indexer 100 should scan all blocks starting from 100 to the latest, once reached the top it should subscribe to new incoming blocks
• Indexer should scan for all blocks if they don't already exist in the database

Public API

REST API with the following endpoints:

• /block [GET]
• /stats [GET]
• /tx [GET]
• /index [POST]

Examples:

• /block - returns the latest block and all associated transactions
• /block/100 - returns the block number 100 and all associated transactions
• /stats - returns sum of all amounts and transactions
• /stats/100:200 - return sum of all amounts and transactions between blocks 100 and 200
• /tx - return latest transaction
• /tx/0x... - return the transactions with the specified hash
• index/?auth_token&scan=100:200 - instructs our service to trigger indexer for a fresh scan of blocks between 100 and 200