Problem performance mongo 4.0, concurrencies and locking


i am a newbie with mongo, i use mongo 4.0 on two server, i have problem performance of lot of queries concurrencies and lot of intent locks r/w, some are expired after a time limit of 30s aftre 2000 retryies acquirecount lock read.

If i test on my pc and local base, the requests work less than 1ms with index on database copie (5 millions documents), some parameters limite seem violated in mongod instance. but on production, i have lot of latencies on execution queries.

My question, is how know the limit worker on mongod instance, the max number of queries/insert/update command, pool queue, connexion max concurrencies on database, and i check that, which paramter i can use…
i read faq en concurrencie/lock but that doesnt help so much

is the insertOne/insertMany command lock and block the collection to the queries ?

i need more tools or way to check/set that in real life

thanks your information