jm + expiry   4

_Optimal Probabilistic Cache Stampede Prevention_ [pdf]
'When a frequently-accessed cache item expires, multiple requests
to that item can trigger a cache miss and start regenerating
that same item at the same time. This phenomenon,
known as cache stampede, severely limits the performance
of databases and web servers. A natural countermeasure to
this issue is to let the processes that perform such requests
to randomly ask for a regeneration before the expiration
time of the item. In this paper we give optimal algorithms
for performing such probabilistic early expirations. Our algorithms
are theoretically optimal and have much better
performances than other solutions used in real-world applications.'

(via Marc Brooker)
via:marcbrooker  caching  caches  algorithm  probabilistic  expiration  vldb  papers  expiry  cache-miss  stampedes 
6 weeks ago by jm
Manage DynamoDB Items Using Time to Live (TTL)
good call.
Many DynamoDB users store data that has a limited useful life or is accessed less frequently over time. Some of them track recent logins, trial subscriptions, or application metrics. Others store data that is subject to regulatory or contractual limitations on how long it can be stored. Until now, these customers implemented their own time-based data management. At scale, this sometimes meant that they ran a couple of Amazon Elastic Compute Cloud (EC2) instances that did nothing more than scan DynamoDB items, check date attributes, and issue delete requests for items that were no longer needed. This added cost and complexity to their application. In order to streamline this popular and important use case, we are launching a new Time to Live (TTL) feature today. You can enable this feature on a table-by-table basis, specifying an item attribute that contains the expiration time for the item.
dynamodb  ttl  storage  aws  architecture  expiry 
february 2017 by jm
The problems with forcing regular password expiry

The new password may have been used elsewhere, and attackers can exploit this too. The new password is also more likely to be written down, which represents another  vulnerability. New passwords are also more likely to be forgotten, and this carries the productivity costs of users being locked out of their accounts, and service desks having to reset passwords.
It’s one of those counter-intuitive security scenarios; the more often users are forced to change passwords, the greater the overall vulnerability to attack. What appeared to be a perfectly sensible, long-established piece of advice doesn’t, it turns out, stand up to a rigorous, whole-system analysis. CESG now recommend organisations do not force regular password expiry.
cesg  recommendations  guidelines  security  passwords  expiry  uk  gchq 
april 2016 by jm

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