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Post by naturalselection on Aug 18, 2015 17:18:29 GMT
As a software engineer, could someone from Saving Stream please explain how loans can get in a state of over subscription?
It implies atomic database transactions aren't being used, which is worrying for any platform dealing with financial services. Is human intervention used to rebalance deposits and loan allocation?
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Liz
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Post by Liz on Aug 18, 2015 17:21:58 GMT
I blame the bots!
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ilmoro
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'Wondering which of the bu***rs to blame, and watching for pigs on the wing.' - Pink Floyd
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Post by ilmoro on Aug 18, 2015 17:27:48 GMT
Clearly time for some smacked bot(ties)! 
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Post by naturalselection on Aug 18, 2015 17:40:58 GMT
All jokes aside, even automated loan buying and selling would be mitigated if they performed actions using transactions, regardless of how many active (concurrent) users are hitting the databases.
I do like Saving Stream, but any financial platform that even gives a hint of not using atomic transactions is a bit scary.
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webwiz
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Post by webwiz on Aug 18, 2015 17:56:58 GMT
All jokes aside, even automated loan buying and selling would be mitigated if they performed actions using transactions, regardless of how many active (concurrent) users are hitting the databases. I do like Saving Stream, but any financial platform that even gives a hint of not using atomic transactions is a bit scary. Sorry to be dim but I do not understand. can you elucidate? If bots are bidding can't they put in bids faster than the server can process them?
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adrianc
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Post by adrianc on Aug 18, 2015 18:04:04 GMT
All jokes aside, even automated loan buying and selling would be mitigated if they performed actions using transactions, regardless of how many active (concurrent) users are hitting the databases. I do like Saving Stream, but any financial platform that even gives a hint of not using atomic transactions is a bit scary. I think what's happening is that if there's <say> £500 available in a loan, and two people click to buy whilst their page says "£500 available" then, rather than say to one "Ooh, sorry - you're out of luck, it got nabbed from under your nose", SS will sell it to both. They'll then have -£500 available, until the next time somebody sells some. Then the first £500 will "clear the overdraft", and anything left goes on the market. It's the only explanation that makes sense to me, other than rampant cock-up.
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jonbvn
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Post by jonbvn on Aug 18, 2015 18:18:39 GMT
All jokes aside, even automated loan buying and selling would be mitigated if they performed actions using transactions, regardless of how many active (concurrent) users are hitting the databases. I do like Saving Stream, but any financial platform that even gives a hint of not using atomic transactions is a bit scary. I think what's happening is that if there's <say> £500 available in a loan, and two people click to buy whilst their page says "£500 available" then, rather than say to one "Ooh, sorry - you're out of luck, it got nabbed from under your nose", SS will sell it to both. They'll then have -£500 available, until the next time somebody sells some. Then the first £500 will "clear the overdraft", and anything left goes on the market. It's the only explanation that makes sense to me, other than rampant cock-up. Thank you for an this explanation, which seems eminently plausible. As a SS noob, I really was wondering about the negative loan availability numbers. TBH, from what I have seen over the last few days does not encourage me to invest a significant amount at this time.
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kermie
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Post by kermie on Aug 18, 2015 18:19:19 GMT
All jokes aside, even automated loan buying and selling would be mitigated if they performed actions using transactions, regardless of how many active (concurrent) users are hitting the databases. I do like Saving Stream, but any financial platform that even gives a hint of not using atomic transactions is a bit scary. I think what's happening is that if there's <say> £500 available in a loan, and two people click to buy whilst their page says "£500 available" then, rather than say to one "Ooh, sorry - you're out of luck, it got nabbed from under your nose", SS will sell it to both. They'll then have -£500 available, until the next time somebody sells some. Then the first £500 will "clear the overdraft", and anything left goes on the market. It's the only explanation that makes sense to me, other than rampant cock-up. As an IT geek, I can confirm that this should not happen, as naturalselection points out. There should be database locks ("transactions") such that only one person gets the sale. The techniques to ensure this is done correctly are very well understood in IT.
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adrianc
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Post by adrianc on Aug 18, 2015 18:22:12 GMT
I think what's happening is that if there's <say> £500 available in a loan, and two people click to buy whilst their page says "£500 available" then, rather than say to one "Ooh, sorry - you're out of luck, it got nabbed from under your nose", SS will sell it to both. They'll then have -£500 available, until the next time somebody sells some. Then the first £500 will "clear the overdraft", and anything left goes on the market. It's the only explanation that makes sense to me, other than rampant cock-up. As an IT geek, I can confirm that this should not happen, as naturalselection points out. There should be database locks ("transactions") such that only one person gets the sale. The techniques to ensure this is done correctly are very well understood in IT. As another IT geek, I think we're seeing a deliberate (if odd) design decision. If you see the loan page with some available, you can buy it. It will be available. Once you start the transaction to buy that part, the transaction is atomic.
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kermie
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Post by kermie on Aug 18, 2015 18:35:21 GMT
As another IT geek, I think we're seeing a deliberate (if odd) design decision. If you see the loan page with some available, you can buy it. It will be available. Once you start the transaction to buy that part, the transaction is atomic. Yes - that is probably how it is implemented, hence you end up with -ve amounts left. But I doubt it is deliberate - I can't imagine anyone consciously doing it this way. The genuinely "transactional" approach (where you never "oversell" anything) means that the "transaction" does not start until well after the user confirms that he really wants to buy the loan part (the final HTTP POST). At that point the user needs to accept that it can still get rejected at the server (if someone else got there first) - this is occasionally less pleasing from a user perspective (he receives a "last minute decline"), but happens very rarely. The formal transaction should not actually start until the HTTP POST hits the server and the request thread acquires some database lock. I'm very much hoping SS understand this and are looking to resolve it on the new platform. IN EDIT: of course, you *might* choose to do it the "broken" way if you can't scale your database sensibly - if implemented poorly, the the locking could have a non-trivial performance hit. Given today's carry-on, I can't but smirk at that :-)
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Post by yorkshireman on Aug 18, 2015 18:41:52 GMT
That sums up the whole farce.
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Post by yorkshireman on Aug 18, 2015 18:49:24 GMT
As another IT geek, I think we're seeing a deliberate (if odd) design decision. You're being too kind. It's very poor design. A system like that implemented in a real market would cause chaos since the seller would find themselves short of a loan they can't be short of. The seller would not be able to deliver the loan and would default. QED. We are entrusting our money to an unprofessional firm, which I personally find rather worrying.
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adrianc
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Post by adrianc on Aug 18, 2015 19:02:09 GMT
As another IT geek, I think we're seeing a deliberate (if odd) design decision. You're being too kind. It's very poor design. Let's just say it's not necessarily the way I'd do it... Except they _can_ be short. And they frequently (permanently) are. There's £37.3m of loans out there. SS are paying 12% interest on that - they MUST be charging more. Let's say 14%. So they're paying out just under £4.5m in interest, but receiving just over £5.2m. £700k - plus whatever else in fees - in margin. Against that, they're currently - at the end of an afternoon of utter chaos - just under seven grand short. That's £800 plus shrapnel of interest, if we assume that's the annual average short position. £800 vs £700k. I think the margin can cope with the short, don't you?
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jonah
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Post by jonah on Aug 18, 2015 19:21:18 GMT
I think that SS says they charge 1.5% per month on their site somewhere.
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Post by pepperpot on Aug 18, 2015 19:29:45 GMT
The SS site was designed and put live when there were (when I first signed up in 2013) less than half a dozen boat loans with availability in all of them and they were max £50k. I think that little site (with slightly informal allocating due to this being loaned to SS, not the borrower directly) has coped remarkably well 'till now. I think everyone is in agreement that the new site is needed sooner rather than later.
(I just hope it works, as 're-vamped P2P site fatigue' is setting in)
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