Account Filter (memcmp / dataSize)

Optional filter objects passed to getProgramAccounts that narrow results by comparing raw bytes in account data. A memcmp filter specifies a byte offset and an expected bytes value (base58 or base64 encoded), enabling field-level matching such as filtering all token accounts by a specific mint address; a dataSize filter restricts results to accounts whose data length equals an exact byte count. Combining both filters is the standard pattern for efficiently querying discriminated Anchor accounts or specific SPL token account sets.