Simultaneos transactions can cause race conditions in solana programs?

Question

Simultaneous transactions could cause race conditions on a Solana program? For instance if we have the following counter example:

#[account]
pub struct Counter {
    pub number: u8,
}

#[derive(Accounts)]
pub struct UpdateCounter<'info> {
    pub payer: Signer<'info>,
    #[account(mut)]
    pub counter: Account<'info, Counter>,
}

pub fn update_counter(ctx: Context<UpdateCounter>) -> Result<()> {
    let counter = &mut ctx.accounts.counter;
    counter.number = counter.number + 1;
    Ok(())
}

And many users call update_counter() at the same time which would be the outcome? would it cause some transactions to fail? would the last transaction overwrite the number written by the previous user? Or would it work normally (No race conditions)?

Answer 1

Because the update_counter function doesn't take an argument, only an account, each transaction in the same block will just increment the counter by 1. So if you call 5 update_counter instructions / transactions in the same block, it will be 5 at the end of the block.