Understanding Pre and Post Balance Checks on Solana: A Developer's Guide

As a developer working with blockchain and cryptocurrency, it is important to understand the complexities of validating user payments on platforms like Solana. In this article, you will learn how to perform pre and post balance checks as part of a transaction (tx) on Solana.

What is a presale?

On most blockchain platforms, including Solana, balances refer to the amount of value or tokens an account has stored in its wallet. Pre balances occur before the user makes transactions, while post balances occur after the user makes payments.

As part of a transaction on Solana, pre and post balances are used as a security measure to prevent tampering with user funds. This is especially important when users make multiple payments in the same block.

Pre-payment balance check

A prepayment balance check is performed by comparing the expected balance (pre-payment balance) with the current balance (post-payment balance). If there is a match, the transaction is considered valid and can be processed immediately.

Here are some examples of scenarios where prepayment balance checks may fail:

• 
  Multiple payments in the same block: When users make multiple transactions in the same block, the pre-payment balance check may not correctly account for all individual balances.

• 
  Invalid or stale balance: If a user's balance is stale (e.g. due to a transaction that has not yet been processed), the pre-payment balance check may return an incorrect result.

Post-payment balance inquiry

A post-payment balance check is performed by comparing the current balance (post-payment balance) with the expected balance (pre-payment balance). If they don't match, the transaction is considered invalid and may be rejected by the network or wallet.

Here are some scenarios where a post-balance check may fail:

• 
  Balance discrepancies: Even if preliminary balances are correct, balance discrepancies can occur, for example due to:

• Network congestion

• Transaction errors (e.g. block rejection)

• Wallet errors

• 
  Preliminary balance updates: If a user's account is updated with new balances, these changes may not be detected in the subsequent balance check.

Best practices for pre- and post-balance checks on Solana

To minimize risk and ensure reliable transactions:

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  Use atomic operations: When making multiple transactions in the same block, use atomic operations to ensure each transaction is processed independently.

• 
  Verify balance updates: Periodically check balances to see if they match expected values ​​after a user makes transactions or receives payments.

• 
  Implement robust error handling: Properly handle errors and exceptions, including those related to provisional and subsequent balances.

Conclusion

Pre-issue balance verification is an important security measure on Solana and helps prevent tampering with user funds. By understanding the impact of multiple payments in the same block and implementing best practices for post-issue balance verification, developers can ensure reliable transactions and maintain user trust in their applications.