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Migrating Uber's ledger data from DynamoDB to LedgerStore

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Re: Migrating Uber's ledger data from DynamoDB to LedgerStore

#21
post #19

Earlier quoted context omitted.

Still, they have 10B rides in 2023 including Eats, say 75-100B since inception. What would be a record such that each transaction needs 10-15 on average?

Consider it might be quite de-normalized as typical at scale. Some records for the customer, some for the driver, some for the restaurant...

You might even have a few more.

Eg you might have a record for each stage of the meal. When it's ordered, when it's cooked, when it's delivered, etc.

Re: Migrating Uber's ledger data from DynamoDB to LedgerStore

#23
post #3

Earlier quoted context omitted.

1T "records". Any given transaction can have N records. I'm assuming this includes Uber Eats as well.

Still, they have 10B rides in 2023 including Eats, say 75-100B since inception. What would be a record such that each transaction needs 10-15 on average?

> What would be a record such that each transaction needs 10-15 on average?

Does it have to be 1-dimensional? Depends exactly what payments is. There are refunds, discounts, paying e.g. drivers. There are also things like monthly subscriptions people can subscribe to for discounts / unlimited uses. Lots of things add up.

Re: Migrating Uber's ledger data from DynamoDB to LedgerStore

#26
post #10

Congrats to anyone who worked on it! However, I'm guessing the cost of just running this team be quite large and not significantly different from the savings (6M), and add on top of it the overhead of maintenance. Payments would not likely be a long-term bet as well, so kind of interesting why teams take up such projects ? Is it some kind of sunk-cost with the engineering teams you already have?

The estimate sounds suspiciously similar to just the data storage component of DynamoDB. 1.7PB of data and indexes is about $5.1m/year in DynamoDB storage at list.

Supporting that, Uber’s blog post linked from the article mentions cost savings as a benefit from going from three systems to one, and doesn’t really mention any dollar figure afaict.

https://www.uber.com/en-AU/blog/migrating-from-dynamodb-to-l...

Re: Migrating Uber's ledger data from DynamoDB to LedgerStore

#27

Congrats to anyone who worked on it! However, I'm guessing the cost of just running this team be quite large and not significantly different from the savings (6M), and add on top of it the overhead of maintenance. Payments would not likely be a long-term bet as well, so kind of interesting why teams take up such projects ? Is it some kind of sunk-cost with the engineering teams you already have?

> I'm guessing the cost of just running this team be quite large and not significantly different from the savings (6M), and add on top of it the overhead of maintenance

I'm guessing they know a lot about their costs, and you know very little. There's little value in insulting the team members like this.

Re: Migrating Uber's ledger data from DynamoDB to LedgerStore

#28
Is this another outlier when you reach certain scale, it’s more beneficial to roll your own? Pretty amazing what Uber has to deal with.

Also it’s not very clear from the original articles, what is the new total “cost of ownership” of this new refactored service. Like now they need to manage their own databases and the storage backing them. Or did i miss it?

Re: Migrating Uber's ledger data from DynamoDB to LedgerStore

#29
post #18

I wonder if 1.7 petabytes of data (1T indexed records) could fit on a single (very) beefy baremetal server for under a couple thousand dollars a month, served by SQLite. Like this: https://use.expensify.com/blog/scaling-sqlite-to-4m-qps-on-a...

Given 30.7TB SSD’s are about $5500 each and you’d need 56 to to get to 1.7PB (with no redundancy). Not to mention that SQLite’s maximum DB size is 140TB.

I don’t think you’d be able to fit this much storage into a single machine, especially not for a few thousand a month and SQLite wouldn’t be appropriate for this use-case.

Re: Migrating Uber's ledger data from DynamoDB to LedgerStore

#30

I’m working on a specialized data store[1] that would be perfect for this kind of use case (large “cold” storage with indexing). But I’m having trouble finding potential customers. I’ve tried Google search ads but got 99% spam and 1% potential investors, but 0% potential customers. If anybody has any ideas I’m all ears. 1. https://www.haystackdb.dev/

You need to be doing enterprise sales not marketing. There is a lot of advice here and in general on that but you definitely need to be making calls with that type of business.

Yep nobody with the problem you’re offering to solve is going to solve it by googling and picking some random company they’ve never heard of with no track record.
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