1 00:00:00,120 --> 00:00:01,390 So here is a new feature 2 00:00:01,390 --> 00:00:03,660 of DynamoDB called Transactions. 3 00:00:03,660 --> 00:00:05,640 It's a new feature from November 2018. 4 00:00:05,640 --> 00:00:07,480 So it should appear in the exam very soon. 5 00:00:07,480 --> 00:00:09,400 And a transaction is the ability 6 00:00:09,400 --> 00:00:13,261 to create, update or delete multiple rows in multiple tables 7 00:00:13,261 --> 00:00:15,030 at the same time. 8 00:00:15,030 --> 00:00:17,900 It's very familiar to what a transaction is in RDBMS 9 00:00:17,900 --> 00:00:18,850 such as PostgreSQL. 10 00:00:19,690 --> 00:00:23,040 So it's called Transactions because it's an all or nothing 11 00:00:23,040 --> 00:00:24,310 type of operation. 12 00:00:24,310 --> 00:00:26,430 That means that, either all the things you said 13 00:00:26,430 --> 00:00:27,960 as per that transaction happen. 14 00:00:27,960 --> 00:00:29,810 Either none of them happen. 15 00:00:29,810 --> 00:00:33,150 This is the main feature of a transaction here. 16 00:00:33,150 --> 00:00:34,370 So now for the Write Modes. 17 00:00:34,370 --> 00:00:35,650 We know the Standard Write Mode, 18 00:00:35,650 --> 00:00:37,890 but now there's a new Write Mode called Transactional. 19 00:00:37,890 --> 00:00:40,220 And for the Read Mode we know Eventual Consistency, 20 00:00:40,220 --> 00:00:41,790 we know Strong Consistency, 21 00:00:41,790 --> 00:00:44,907 but now there is Transactional as a new Read Mode. 22 00:00:44,907 --> 00:00:47,040 So, for the Transactional Mode, 23 00:00:47,040 --> 00:00:51,107 it Consumes twice the WCU or RCU that you know of. 24 00:00:51,107 --> 00:00:52,947 No calculations should be expected of you. 25 00:00:52,947 --> 00:00:56,010 The only thing is, that is expected of you 26 00:00:56,010 --> 00:00:57,480 is to remember what the transaction is, 27 00:00:57,480 --> 00:00:59,230 and in which case you will use it. 28 00:00:59,230 --> 00:01:00,730 So how about we go through an example. 29 00:01:00,730 --> 00:01:02,430 And this is just a theory lecture. 30 00:01:02,430 --> 00:01:04,980 So let's say we have an Account Balance Table. 31 00:01:04,980 --> 00:01:08,240 And the Account Balance Table has the account id, 32 00:01:08,240 --> 00:01:11,140 the balance, the money the user has in their account, 33 00:01:11,140 --> 00:01:13,740 and the last transaction timestamp. 34 00:01:13,740 --> 00:01:15,520 Now so there is a Bank Transaction Tables, 35 00:01:15,520 --> 00:01:17,440 which represents the transactions 36 00:01:17,440 --> 00:01:19,120 maybe between the accounts. 37 00:01:19,120 --> 00:01:21,450 So here we can see that we have two transactions 38 00:01:21,450 --> 00:01:22,283 between these two accounts. 39 00:01:22,283 --> 00:01:24,147 And we can see the value of these transactions. 40 00:01:24,147 --> 00:01:27,070 Obviously, if I wanted update, 41 00:01:27,070 --> 00:01:29,740 and add a bank transaction to a table, 42 00:01:29,740 --> 00:01:31,960 I also want to add that to my Account Balance Table 43 00:01:31,960 --> 00:01:33,300 at the very same time. 44 00:01:33,300 --> 00:01:34,641 I don't want an update to happen 45 00:01:34,641 --> 00:01:35,880 to the Bank Transaction Tables 46 00:01:35,880 --> 00:01:37,800 and not happen to the Account Balance. 47 00:01:37,800 --> 00:01:40,360 So we need either both things to happen, 48 00:01:40,360 --> 00:01:42,540 both Writes to happen to both tables 49 00:01:42,540 --> 00:01:43,373 or none of it. 50 00:01:43,373 --> 00:01:46,330 And this is a perfect use case for transaction. 51 00:01:46,330 --> 00:01:49,773 So transaction again is a Write to both tables, or none. 52 00:01:49,773 --> 00:01:52,870 And hopefully that clarifies the concept for you. 53 00:01:52,870 --> 00:01:54,430 So it's not something you can do for the console 54 00:01:54,430 --> 00:01:55,910 but it's something you need to be know about. 55 00:01:55,910 --> 00:01:58,130 And for the exam, probably just a high level. 56 00:01:58,130 --> 00:01:59,320 So I hope that was helpful 57 00:01:59,320 --> 00:02:01,270 and I will see you in the next lecture.