[1ba9115454]

This is probably the best mini implementation I've seen so far. The code is hosted at https://github.com/Haseeb-Qureshi/lets-build-a-blockchain

He's missed one thing though, which a lot of these small implmentations miss, its the code for chain re-org.

https://en.bitcoin.it/wiki/Chain_Reorganization

This is a crucial piece of code that figures out which chain is correct if 1 or more blocks arrive that have a greater proof of work than your current best chain.

But otherwise, a very good attempt.

[xiphias]

As far as I saw the whole blockhain is serialized and sent to the peers, so taking care of chair reorgs is trivial (and done in the video). What's really missing is difficulty retargeting.