How many are operational? I think they need at least 200 to fend off a potential Japanese threat in the east.
What japanese threat?
Japanese fighters would be shot down with S-400s and their ships sunk by Bal and Bastion before they even get close... those Su-35s would have very little to actually do.
Checkmate will be a very good solution to increase numbers. In Syria they quickly learned that twin-engines are often over-kill and too expensive for most missions.
What they found was that big Sukhois are expensive to operate in large numbers and that smaller lighter aircraft could often do quite a few jobs more efficiently and affordably.
The MiG-35 is much cheaper to operate than any model Flanker which is why they are buying some for testing and evaluation.
What they also need is r-77M retrofited to su-35/30.
Should be compatible as it was Su-35, MiG-35 and Su-57 that the missile was designed for.
The Russian MoD assessed the situation and decided that a few fighter jets and A2/AD systems was all that is needed to keep any Japanese forces in check.
Agreed... actually sending 200 heavy fighters to the Far East would likely drive the Japanese to respond by increasing their forces and creating an arms race where there was no need for one.
And a AESA Radar instead of an PESA this in combination with the retro-fitting of the R-77M would make it very, very potent. Instead they've kept producing the same production model there's no new things to it's batches?
A lot of the advantages of electronic scanning make the cheaper simpler PESA a powerful radar system, while the AESA is more capable it is also much more expensive, and in many areas the differences are not so obvious.
There is little value in making a radar ten times more expensive if it does not improve performance or capabilities very much at all.
Now all of that is in production for the su-57 so they will buy the su-57 instead of making an expensive su-35 with su-57 technology.
They will likely use both and try to unify a lot of the systems used to reduce costs and improve commonality.
If it turns out that the Su-35 is cheaper to operate then they might keep using those for a range of roles where stealth is meaningless, but if it turns out the cost is not so different and the Su-57 is much better then they might go the other way.
The point is that both are in production and they get to choose which is best... they are not driven by doctrine that demands an all stealth fighter fleet by x date no matter what the costs.
Like I've been saying all this time, Su-35 is a placeholder for Su-57
They needed a new stealth fighter to fight western stealth fighters, but they didn't know how effective they might be or how many they might need.
Even the US can't afford an all stealth fighter fleet and I doubt the Russian AF would even want to try to do the same.
The Checkmate and anything MiG comes up with will be along the lines of affordable 5th gen medium to light fighter and that will most likely end up being the numbers aircraft... along with unmanned drones of course.