Why not make one big smart contract with all functionality and deploy it?

[AnandK-2024]

When one contract calling a function on another contract — known as an external function call — is expensive (little more than 2600 gas.)

Why not make one big smart contract with all functionality and deploy it?

That would remove all the gas created by contracts calling external functions on other contracts. One problem with this is that there is a limit to how large a single contract can get. The code of a smart contract is compiled into a mass of data called bytecode and the bytecode is what is deployed and stored on a blockchain. The maximum size of a smart contract’s bytecode is 24.5KB. So that limits how much functionality can exists in a smart contract.

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