Analyze and optimize: Slow queries

[patphongs]

What we're after:
To make our website more efficient, we need to debug and performance tune by optimizing slow queries that are most frequently used

Completion criteria:

• Analyze top 10 slowest queries and base the results against how many times those queries are called. This should lead us on our decisions on which queries to work on first. Take a look at the top 10 slow queries here: https://docs.google.com/spreadsheets/d/1U0EIRbFSuNWJC5uvcb54Sv6KTRnokSSb87Zd_4ZhjrY/edit#gid=0
• Optimize the slowest and most frequently used queries
• Implement the optimization

[patphongs]

Two additional tickets have been created by @pkfec for optimizing Schedules A & B. Closing this issue in favor of those:

#3383
#3384