I want to use a QFX10002-36Q with 4x Full table and 2x IXP and total received routes from all of them will be around 3.6-4 Milion routes, QFX10002-36Q datasheet said that this switch can hold 10M RIB IPv4 routes and 4Milion IPv6 routes and a totally 2M IPv4/IPv6 routes in FIB. referring to the juniper documents it can hold my full tables in RIB then it will install best path on the FIB (best paths from all neighbours are around 900K) and I do not have IPv6. so there will be no problem if I want to use this switch in this scenario, do I understand this correctly?
According to the juniper system overview the switch has 16Gb of RAM.
As of today the Internet IPv4 full table is around 850 000 routes.
So, yes the switch can handle 4 times the full table without issues.
Note that even if you don't plan to use IPv6 today, it's better to take it into account to be able to add it later (and the sooner the better).