A 2020 update:
- YQL was terminated on Jan, 3, 2019
Because of this, the older answers in the questions are no longer valid.
Archive has a backup of the link they mention from the day before the shutdown
You’ll probably never need it, the limits have been changed anyway - Yahoo finance itself was also stopped for a while, but it’s available again.
It’s located at https://query1.finance.yahoo.com/v7/finance (e.g. https://query1.finance.yahoo.com/v7/finance/quote?symbols=AMZN) - I also wondered about the new limits but I can’t find an official answer. Online everyone seems to have another answer, but it general it boils down “a 4 digit number” every hour when using the unauthenticated (free) version.