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Now let's talk about Amazon QLDB,

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which stands for Quantum Ledger Database.

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So what is it?

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A ledger is a book recording financial transactions

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and so QLDB is going to be just to have a ledger

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of financial transactions.

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It's a fully managed database, it's serverless,

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highly available, and has replication of data

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across three availability T zones.

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And it's used to review history of all the changes

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made to your application data over time,

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that's why it's called a ledger.

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So it's an immutable system as well,

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that means that once you write something to the database,

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it can not be removed or modified.

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And there is also a way to have a cryptographic signature

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to make sure that indeed nothing has been removed.

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So how does it work?

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Well, there is behind the scenes a journal,

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and so a journal has a sequence of modifications.

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And so anytime a modification is made,

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there is a cryptographic hash that is computed

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which guarantees that nothing has been deleted or modified

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and so this can be verified by anyone using the database.

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So this is extremely helpful for financial transactions

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because you wanna make sure that

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obviously no financial transaction

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is disappearing from your database

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which makes QLDB a great ledger database in the cloud.

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So you get two to three times better performance

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than common ledger blockchain frameworks

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and also you can manipulate data using SQL.

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Now, as you'll see in the next lecture

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there's also another database technologies

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called Amazon Managed Blockchain.

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But the difference between QLDB and Managed Blockchain

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is that with QLDB, there is no concept of decentralization.

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That means that there's just a central database

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owned by Amazon that allows you to write this journal.

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Okay.

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And this is in line with many financial regulation rules.

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So the difference between QLDB and Managed Blockchain

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is that QLDB has a central authority component

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and it's a ledger, whereas managed blockchain

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is going to have a de-centralization component as well.

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Okay.

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So that's it, anytime you see financial transactions

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and ledger, think QLDB.

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I will see you in the next lecture.