Algorand finalizes every block the moment it lands

Bitcoin users are accustomed to waiting. Because a freshly mined block can still be orphaned when the network settles on a longer chain, the convention is to wait for several confirmations before treating a transaction as settled. @Algorand is built around a different premise: the wait should not exist at all.

How the three-step protocol works

Each consensus round on Algorand runs through three stages: propose, soft vote, and certify. Consensus requires three steps to propose, confirm, and write the block to the blockchain, according to the Algorand developer documentation. A single node proposes a block, a randomly selected committee soft-votes to filter competing proposals, and a second committee issues a certify vote that locks the block in permanently.

The key to making this work without creating a target for attackers is cryptographic sortition. Algorand's implementation randomizes a new subset of members for each step of block commitment using a Verifiable Random Function (VRF), and only the nodes selected for the next consensus step know they are selected, while other nodes can only verify this membership selection afterwards. Committee membership is weighted by stake, so larger holders carry proportionally more influence, but no attacker knows who will be on the committee until a user actually speaks.

Unlike many major blockchains, Algorand does not fork. A transaction is considered permanent as soon as it is included in a block. This delivers instant finality with sub-3 second block latency and around 10,000 transactions per second.

The trade-off: stall, not fork

The design comes with a deliberate trade-off. Since Algorand is pure proof-of-stake and uses a voting mechanism to validate blocks, forking is impossible. In a worst-case scenario, if the committee is taking longer to reach agreement, the blockchain will slow down or temporarily stall. In other words, Algorand prefers to pause rather than split, accepting a temporary slowdown in exchange for an absolute guarantee that no confirmed transaction will ever be reversed.

For most applications, that trade-off is attractive. Because Algorand does not fork, transactions are final as soon as they are confirmed in a block, meaning a throughput of 10,000 TPS actually represents 10,000 fully finalized transactions per second. On Bitcoin, the equivalent figure carries an asterisk until enough confirmations have accumulated.

The security model rests on one core assumption: the network can tolerate malicious actors and avoid forks and double-spending as long as a supermajority of the stake, over two-thirds, is held by honest participants.

Sources:
Algorand: Pure Proof-of-Stake consensus explained
Algorand Developer Portal: Algorand consensus
Algorand Developer Portal: Why Algorand?