Timelock pattern in Blockchain / Solidity - Step-by-Step Execution

Concept Flow - Timelock pattern

Start

↓

Request Action

↓

Set Timelock Expiry

↓

Wait Until Expiry

↓

Check Current Time >= Expiry?

No→Wait

Yes↓

Execute Action

↓

End

The Timelock pattern delays execution of an action until a set time has passed, ensuring a waiting period before the action runs.

Execution Sample

Blockchain / Solidity

uint public unlockTime;

function requestAction() public {
  unlockTime = block.timestamp + 1 days;
}

function executeAction() public {
  require(block.timestamp >= unlockTime, "Action is locked");
  // action code
}

This code sets a future unlock time when an action is requested, then only allows execution after that time.

Execution Table

Step	Action	block.timestamp	unlockTime	Condition	Result
1	Call requestAction()	1000000	1000000 + 86400 = 1086400	N/A	unlockTime set to 1086400
2	Call executeAction() at time 1005000	1005000	1086400	1005000 >= 1086400?	False - revert, cannot execute
3	Call executeAction() at time 1086400	1086400	1086400	1086400 >= 1086400?	True - action executes
4	Call executeAction() at time 1086500	1086500	1086400	1086500 >= 1086400?	True - action executes

💡 Execution stops if current time is less than unlockTime; action only runs after unlockTime.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
unlockTime	0	1086400	1086400	1086400	1086400
block.timestamp	N/A	1000000	1005000	1086400	1086500

Key Moments - 3 Insights

Why can't executeAction run immediately after requestAction?

Because unlockTime is set to a future timestamp (current time + 1 day). The execution_table row 2 shows the condition fails when current time is less than unlockTime.

What happens if executeAction is called exactly at unlockTime?

The condition block.timestamp >= unlockTime is true, so the action executes successfully as shown in execution_table row 3.

Does the unlockTime change after it is set?

No, unlockTime stays the same until requestAction is called again. The variable_tracker shows unlockTime remains constant after step 1.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of unlockTime after calling requestAction()?

A 1000000

B 1086400

C 0

D 1005000

💡 Hint

Check execution_table row 1 under unlockTime column.

At which step does the condition block.timestamp >= unlockTime become true for the first time?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

See execution_table Condition and Result columns for each step.

If the unlockTime was set to current time + 2 days instead of 1 day, how would step 2 change?

A Condition would still be false at step 2

B unlockTime would be less than block.timestamp

C Condition would be true at step 2

D executeAction would execute immediately

💡 Hint

Compare unlockTime and block.timestamp values in execution_table row 2.

Concept Snapshot

Timelock pattern delays actions until a set future time.
Set unlockTime = current time + delay.
Only allow execution if current time >= unlockTime.
Prevents immediate execution, adds security delay.
Common in blockchain governance and contracts.

Full Transcript

The Timelock pattern is a way to delay an action in a blockchain contract until a certain time has passed. First, when an action is requested, the contract sets a future unlockTime by adding a delay (like 1 day) to the current block timestamp. Then, when trying to execute the action, the contract checks if the current time is at or past the unlockTime. If not, the action is blocked. This ensures a waiting period before the action runs, adding security and transparency. The example code sets unlockTime in requestAction and requires the current time to be greater or equal in executeAction. The execution table shows that calling executeAction too early fails, but succeeds once the unlockTime is reached or passed. Variables like unlockTime stay fixed until reset. This pattern is useful to prevent sudden changes or actions in blockchain systems.