Limitations

Before using ZK Compression to scale your application state, you should consider the limitations of compressed accounts:

General Recommendation

Consider which accounts in your application benefit from ZK Compression, and which don't. You can use both types for different parts of your application!

You may prefer the account not to be permanently compressed if:

  • The account gets updated very frequently within a single block (e.g., shared liquidity pools in a DeFi protocol)

  • You expect the lifetime number of writes to the same account to be very large (>>1000x)

  • The account stores large amounts of data, and you need to access a large part of it (>1kb) inside one on-chain transaction.

Larger transaction size

Solana's Transaction size limit is 1232 Bytes. Transactions exceeding this limit will fail.

ZK Compression increases your transaction size in two ways:

  • 128 Bytes for the validity proof constant size per transaction if you read from at least 1 compressed account.

  • You must send the account data you want to read/write on-chain.

High Compute Unit Usage

System CU usage:

  • ~100,000 CU for validity proof verification this is a constant per transaction if you read data from at least 1 compressed account.

  • ~100,000 CU system use (state tree Poseidon hashing et al).

  • ~6,000 CU per compressed account read/write.

Example: a typical compressed token transfer uses around 292,000 CU.

Higher CU usage can:

  • Lead to usage limits The total CU limit per transaction is 1,400,000 CU, and the per-block write lock limit per State tree is 12,000,000 CU.

  • Require your users to increase their priority fee during L1 congestion Whenever Solana's global per-block CU limit (50,000,000 CU) is reached, validator clients may prioritize transactions with higher per-CU priority fees.

Per-transaction state cost

Each write operation incurs a small additional network cost. If you expect a single compressed account to amass a large amount of state updates, the lifetime cost of the compressed account may be higher than its uncompressed equivalent which currently has a fixed per-byte rent cost at creation.

Whenever a transaction writes to a compressed account, it nullifies the previous compressed account state and appends the new compressed account as a leaf to the state tree. Both of these actions incur costs that add to Solana's base fee.

  • Appending compressed account state to a state tree: Typically ~100-200 lamports per new leaf (2tree_depth×tree_account_rent_cost×rollover_threshold)\left( 2^{\text{tree\_depth}} \times \text{tree\_account\_rent\_cost} \times \text{rollover\_threshold} \right)

  • Nullifying a leaf in a state tree: The current default forester node implementation can nullify one leaf within one Solana transaction (5000 lamports base fee per nullified leaf).

Next Steps

This covers most of the key concepts about ZK Compression! Next, build a program or application with ZK Compression or learn how to set up and run your own node.

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