This is not a duplicate question, as the alarm contract only allows function calls to be made in the future, over a period of at least 10+ blocks...

The current thinking is to just use the alarm clock contract, however, this only allows for a minimum future contract function call of at least 10+ blocks in the future, I need to do it in e.g. 3.

What is the current thinking to invoke a contract function e.g 3 blocks in the future.

Is there anyway to do this, that does not rely on client-side invocation 3 blocks down the track?

I cannot rely on client invocation, I need a definitive, stable, guaranteed way to invoke a function on a smart contract 3 blocks from the time (block) a client had first invoked the contract.

2 Answers 2


Unfortunately, you cannot do this.

  • you need "client invocation" to initiate any kind of transaction in ethereum
  • there is no guarantee whatsoever that your transaction will be mined at a specific time - it is up to the miner to decide whether to include your transaction or not

The fundamental problem with waiting only three blocks for invocation (and the reason I imagine the alarm clock doesn't support it) is that the Ethereum blockchain is very much subject to reorganization at a three block depth. Remember, our block time being only fifteen seconds means we need to wait for more confirmations than a Bitcoin transaction for the same degree of security. Less than 10 minutes, but more than six confirmations.

You could write your own alarm clock contract that supports n-block invocation, but because the alarm contract relies on incentivizing users to send transactions on your behalf, they may choose not to if there is a high risk that their work will go unrewarded. And it very well might not at a three-block depth.

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