Here is the following problem:

email
------
id
email

list
------
id
name

email_to_list
------
email_id
list_id

On `email_to_list` what is your recommendation on how to put indexes. I need to put an UNIQUE on (email_id, list_id). Do i also need to put INDEX on email_id and list_id separately? Presuming i make a lot of JOIN queries on these keys.

Thanks

i would just make them the primary key instead

no!!

primary keys get a unique index by default

but you might add an index on ( list_id , email_id )

this index, along with the primary key index, ensure that all queries will use one or the other index, and both of them are likely to be a covering index