What are the advantages and disadvantages of thinner PCB thickness (&lt;1.6 mm)?

My approach:


Better capacitance interplane and better power decoupling.
Better track-plane coupling.
Problems with assembly process with heavy components
Problems with PCB twist
Extra cost. No standard thickness.


When do you use it? 

Which are the technical limits for assembly thin PCBs (i.e. 0.5mm)? I know that It depends on the size of PCB. Could somebody tell about these limits?


Question: Are mutliple database calls really significant with a network call for a web API?
Answer: If the database is on a different server than your REST service, each database call will result in a network roundtrip and that can significantly hurt performance:

I once observed a single webservice call be translated to about 500 database queries - this was hardly a problem when both the webservice and the database are located on the same machine, but turned into a response time of 6-7 seconds when they were on different machines.    

Obviously, 500 roundtrips to the database is pretty extreme. I'm not sure what your performance requirements are, but as a rule-of-thumb I would say that if you stay under around 10 database queries per REST-call you should not experience a significant performance hit.