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Comment by Jedd | Hacker News Reader

That's a fairly naive expectation.

I had a friend head off in 2011 to work with Hailo in London, and designed much of the data ingest & storage architecture there. That was built on Cassandra, and some of the numbers were staggering, even for a (initially) single-city, < 2,000 driver system.

You're not just tracking start and end point of successful rides -- you're tracking users when their app is open (both drivers and users move around before and after initiating a ride, and you need to share that data between parties), you're also tracking empty vehicles so you can identify over / under serviced areas ... doubtless lots of other real time stuff you want to know. But the big thing is you want to then have that data available for mining, improving your service, regulatory obligations, and so on.

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Only if you believe in retaining all data in perpetuity. I suppose it demonstrates the difference in US and European perspectives on data.

Most of what you describe has little meaning or use at a few months old. Sure you might want to collect detailed awareness of individual drivers over say a month, generic traffic patterns over six months, and little or nothing beyond.

Once the data has outlived that direct, primary, purpose you dispose of it or it's a famous, excessive, data breach waiting to happen. There is absolutely nothing wrong with only keeping billing data beyond say six months max.

> Most of what you describe has little meaning or use at a few months old. Sure you might want to collect detailed awareness of individual drivers over say a month, generic traffic patterns over six months, and little or nothing beyond.

The really invasive pattern-matches happen best retroactively at that scale.

Age of the data does not typically impact many such analyses.

In California, you soon won’t be able to keep 6 months max. You have to hold a year.

> Only if you believe in retaining all data in perpetuity.

There's a huge spectrum between your 'at most 30d' claim in another reply, and 'all data in perpetuity'.

30d is way too short. Perpetuity is probably the idealistic intent, and depending on storage costs over time this may be achievable.

> I suppose it demonstrates the difference in US and European perspectives on data.

How so? I described a the case of one UK-based company, and TFA is about one US-based company, both doing similar things.

> Most of what you describe has little meaning or use at a few months old.

Clearly this is not the case, as evinced by the actions of the people designing, building, operating, and maintaining these types of systems.

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