How to optimize mongo for loads?

Question

MongoDB

In general, when indexing a site, search robots create loads, so much so that the database freezes and pages start to crash on a timeout. How to deal with it? Do not ban the same search engines for indexing.
UPD , it turns out, it's not about loads, because. I go to the console and try to make a simple request, for example, this:

db.articles.find({title:'crimea'})

and that's it, the process hangs, it searches and does not find the article in any way.
Could this be due to the fact that the database has become simply large and it is already difficult for Mongo to quickly take and find an article? What to do in this case and how to be? The database is a copy of Wikipedia, so there is really a lot of data.

Answer 1

indexes in mongo, optimize queries and logic
+ set time when to index only at night
+ set indexing intensity

Answer 2

Is there an index on the title field?db.articles.ensureIndex({title: 1})

title:'crimea'

Is this the exact value of the field, or do you want to search by part of the title (full text search)?