# BlockChain scalability: How does BlockChain process multiple parallel transactions?

I just did some introductory research into blockchain technology and this is a breakdown of my understanding of how it works:

Scenario: Assume Trump wants to send Obama 5 bitcoins. As soon as this transaction is initiated:

1. miners in the peer to peer network will (individually?) start solving for the next valid hash in the block chain. ( does the peer network use the combined processing power to solve together, or do nodes solve individually independent of each other?)

2. Once the valid hash is discovered, the node that did the discovery will be rewarded with a set of bitcoins

3. The ledgers at each node will be updated with the Alice -> Bob transaction, while this newly discovered hash will be a representation of the same. This should approximately take about 10 minutes?

Now there is a good chance my understanding is completely off, but my question is this:

Lets say 1000 transactions are initiated at the same time. Regardless of this, the peer network will be solving for the next hash in the blockchain which will verify 1 transaction. So the 1000 transactions will be verified sequentially as the miners proceed from one valid hash to the next.

If solving for one transaction takes approximately 10 minutes, this would mean to completely verify the 1000 transactions (initiated at the same time) it would take around 1000 x 10 minutes!

Clearly this problem is handled in someway in the real world as i'm pretty sure thousands of bitcoin transactions take place at any given time without a delay like this. Some clarification would be hugely appreciated. thanks!

Following your example what roughly happens is:

As soon as this transaction (tx) is initiated:

1. Peers will receive Trump's tx and propagate the transaction to the rest of the network/peers
2. Peers will do that for the other 999 txs on the network sent at roughly that period
3. The 1000 txs will be aggregated to one block and some of those peers (miners) will try to find a solution (the hash) for that block

a) note that each miner will have some processing power which is a subset of the whole network; thus they try to solve the problem "individually" and in competition from other miners.

b) however, several people can pool processing power behind one miner so a miner can represent hundreds/thousands of people (mining pool).

c) only one miner will get the reward for each block (every ~10 minutes), which will be split among the people that provided processing power to the pool

4. Once the solution is found the whole block (which contains 1000 txs) with the solution is propagated through the network and every peer will validate its correctness. If a peer finds the block valid it will update its blockchain with the new block and thus the 1000 txs will be added to the blockchain and confirmed.

You should probably read up a bit more, but here's some help:

miners in the peer to peer network will (individually?) start solving for the next valid hash in the block chain. ( does the peer network use the combined processing power to solve together, or do nodes solve individually independent of each other?)

Nowadays miners work together in mining pools. These are not part of the actual protocol, but is just the way the mining ecosystem has evolved. As far as the Bitcoin protocol is concerned, you can look at an entire mining pool as an individual miner. Each pool is responsible for trying to make their nodes work in parallel.

Regardless of this, the peer network will be solving for the next hash in the blockchain which will verify 1 transaction

This is where you are wrong. The hash is for a block of transactions, not an individual transaction. For many reasons, it is advantageous to do the proof of work on blocks rather than transactions. See this question for more explanation on that.

I hope this helps.