Wednesday, August 12, 2020

System design: Scaling Memcache at Facebook

 Here is the link. 

I spent near one hour to read the paper, but I do think that it is better for me to get some coaching from a talk. I found two quickly. 

This one should be the great one for me to learn how to scale Memcache at Facebook. 

handling updates

Memcache needs to be invalidated after DB write

Prefer deletes to sets

- idempotent

-demand filled

Up to web application to specify which keys to invalidate after database update

Problems with look-aside caching

stale sets - try to explain this permanent cache key value - until it is deleted

Extend memcache protocol with "leases

- Return and attach a lease-id with every miss

-lease-id is invalidated inside server on a delete

- Disallow set if the lease id is invalid at the server

Need even more read capacity

Incast congestion

memcache - web server 


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