Failure scenarios/bottlenecks

Try to discuss as many failure scenarios/bottlenecks as possible.

1) Additionally, since our system is only eventually consistent, there is a few scenarios where this may not be acceptable. Let's say there is a very famous person who posts a link and within seconds we get 100s of thousands of requests. There are 2 problems here now:

the shortened url hasn't been replicated to all db nodes (especially the ones across the world);

we are getting a thundering herd problem - all of these requests are going to cache miss and all go to the disk which is slow and can cause additional problems/cost in our DB usage.

We can solve this problem by using a "push" based approach in cache for famous/reserve users - we first write in cache and then we write (and replicate) on disk. That would solve the replication/and thundering herd problem, but only if the cache daemon on the application server can have the ability to precisely determine the node id where the cache node with the resource is located.

2) Well, we do have a few things which are SPOF - we can deploy many load balancers, servers, databases nodes, and cache nodes, but we need to be very careful with the algorithm that is generating hashes for the shorter URLs. there is many things that can go wrong:

Submissions

Displaying Solutions with Scores Ranging from 1 to 10

Submissions

Displaying Solutions with Scores Ranging from 1 to 10