The IAVL+ Tree is a sophisticated, versioned, and immutable AVL+ tree data structure, designed for persistent key-value storage in web3 applications, particularly requiring Go 1.18 or higher. This data structure excels in providing a deterministic merkle root hash, essential for securely staging and handling uncommitted transactions. With its balanced structure managed via an adaptive AVL algorithm, the IAVL+ Tree ensures efficient O(log(n)) operations, optimizing transaction processing and storage integrity. Key innovations include storing all data values exclusively on leaf nodes, facilitating streamlined key management and short merkle trails, thus enhancing performance without hashing keys, unlike Patricia tries. The IAVL+ Tree is seamlessly integrated with the Cosmos SDK, leveraging various database interfaces such as tm-db, cometbft-db, and iavl-db across its evolution, ensuring compatibility and performance across different SDK versions. Suitable for blockchain applications, its deterministic hashing approach, albeit order-sensitive, accommodates robust transaction serialization strategies, optimizing both iteration speed and storage efficiency.