Yes, blockchain can be used to store data, and scalable blockchains are increasingly capable of handling large volumes of data with performance that can match, or even exceed, traditional databases like MySQL or PostgreSQL, particularly in terms of security and transaction speed. While blockchain is primarily designed for secure, decentralized, and immutable storage, modern scalable blockchains have evolved to handle larger datasets more efficiently.

For storing customer data, blockchain offers the advantage of enhanced security and transparency. Instead of storing the entire dataset on-chain, which can be costly and inefficient, a common practice is to store essential data or references on the blockchain while keeping larger data sets off-chain. This hybrid approach leverages blockchain's strengths—such as security, immutability, and speed—while allowing you to manage data effectively. To retrieve data, you would query the blockchain for relevant transactions, which can then point to the off-chain data storage.

Blockchain can function as a database, but it differs significantly from traditional databases. Unlike centralized databases, blockchain is decentralized, providing enhanced security and transparency by maintaining an immutable ledger across a network of participants. While ideal for applications requiring high data integrity and transparency, it’s less efficient for tasks needing rapid data processing. Thus, blockchain as a database excels in secure, transparent environments rather than high-speed data handling.

Yes, blockchain can store data, but it’s not the best choice for storing large amounts of customer data like MySQL or PostgreSQL. Blockchain is designed for decentralized, immutable records, making it ideal for things like transaction histories or proof of ownership, but not for storing sensitive personal information or large data sets due to scalability and privacy concerns.

If you want to store customer data, you can use blockchain for storing the data’s cryptographic hash (a fingerprint) rather than the data itself. This way, the actual customer data can be stored off-chain, in a traditional database, and referenced via the blockchain for security and audit purposes. Retrieving the data would involve querying your off-chain database, then verifying it using the blockchain's stored hash.

I was in your shoes when I started learning blockchain too, but once you get the hang of how off-chain and on-chain data work together, it becomes much clearer!