What's preventing the Ethereum blockchain to getting to big too fast

Question

So I recently started looking at Solidity on the Ethereum blockchain, and have a question about the size that smart contracts generate.

I'm aware that there is a size limit for the byte code generated by the contract itself, and that it cannot exceed 27kb. Also there's an upper limit for transactions too. However, what I'm curious about is that, since there's no limit on the variables that smart contract stores, what is stopping those variables from get very large in sizes? For popular smart contracts like uniswap, I would imagine they can generate hundreds of thousands of transactions per day and the state they keep would be huge.

If I understand it correctly, basically every node on the chain would store the whole blockchain, so limiting the size of blockchain would be very important. Is there anything done to limit the size of smart contracts, which mainly I think is dominated by the state variables they store.

Answer 1

Is there anything done to limit the size of smart contracts, which mainly I think is dominated by the state variables they store.

No. Ethereum will grow infinitely and currently there is no viable plan to limit state growth besides keeping transaction costs high and block space premium.

You read more about this in my post Scaling EVM here.

Answer 2

TLDR: The block size limit.

The protocol has a hardcoded limit that prevents the blockchain from growing too fast.

Full Answer

Growth Speed

The protocol measures storage (and computation) in a unit called gas. Each transaction consumes more or less gas depending on what its doing, such that an ether transfer costs 21k gas, but a uniswap v2 swap consumes around 100k gas. Deploying big contracts consume more.

The current gas limit is 30 million per block, so the actual number of transactions varies even if the blocks are always full (some consume more than others).

FYI.: This is why transactions per second is a BS, marketing metric in blockchains with rich smart contracts.

Deeper Dive

Storage as of June 2022

The Ethereum blockchain is currently ~180 GB in size. This is the stuff that is critical to the existence and from which absolutely every thing else is calculated.

Péter Szilágyi is the lead developer of the oldest, flagship ethereum node implementation

That being said, nodes generate a lot of data while processing the blockchain to generate the current state (i.e. how much money do you have on your wallet now).

Today, if you want to run a node that stores every single block and transaction starting from genesis (or what bitcoin, but not ethereum engineers, call an archive node) you currently need around 580 Gb (this grows as the node runs). See Etherscan's geth after they deleting some locally generated data, June 26, 2022.

If you want to run what ethereum engineers call an archive node - a node that not only keeps all blocks from genesis but also does not delete generated data - then you currently need 1.5 TB of storage using erigon.

Older clients that do not use the flat key-value storage, generate considerably more data (in the order of 10TB).

The Future

There are a lot of proposals, research and active development efforts working in parallel and so this part of the answer might become outdated. Here are some of them:

• Sharding: Ethereum will split data (but not execution) into multiple shards, without losing confidence that the entirety of it is available via Data Availability Sampling;
• Layer 2 Technologies: These move gas that was consumed by computation to another layer, without losing guarantees of the first layer such as censorship resistance and security. The two most promising instances of this (on Ethereum) are optimistic and zero-knowledge rollups.
• State Expiry: Registers, Cache, RAM, SSD, HDD, Tape libraries are storage solutions, ordered by from fastest, most expensive to slowest, cheapest. Ethereum will follow the same strategy: move state data that is not accessed often in cheaper places;
• Verkle Trees;
• Portal network;
• State Rent;

Bitcoin's Lightning network is the first blockchain layer 2 technology.