How many database entries can I have before my application begins to become too slow?

How many database entries can I have before my application begins to
become too slow?

References

Reference NO 1

http://stackoverflow.com/questions/15192258/how-many-database-entries-can-i-have-before-my-application-begins-to-become-too

Reference NO 2

http://stackoverflow.com/questions/3716639/what-is-causing-my-access-database-to-be-so-slow

Reference NO 3

http://coding.smashingmagazine.com/2011/03/23/speeding-up-your-websites-database/

Reference NO 4

http://c2.com/cgi/wiki?DatabaseBestPractices

Reference NO 5

http://www.bleepingcomputer.com/startups/

Reference NO 6

http://android.stackexchange.com/questions/35367/my-device-is-getting-slow-apps-start-misbehaving-crashing-what-can-i-do

Reference NO 7

http://dascomputerconsultants.com/DatabaseSlow.htm

Reference NO 8

http://blog.scoutapp.com/articles/2008/07/29/4-simple-steps-to-detect-and-fix-slow-rails-requests