Reasonably well actually. Soldiers and sailors made up the brunt of Soviet military strength during and after the Revolution, of which popular disgust at the war was a major cause. Not just Russian soldiers either--many German and Hungarian POWs had been converted to Bolshevism and were an asset to the revolutionary government.

That didn't mean that they were exempt from the turmoils of a country in revolution. Trotsky's suppression of the Kronstadt Sailors' Soviet was the most famous instance, and being a veteran didn't spare anyone from the Purges.

The above does not necessarily apply to officers or aristocrats. Some Tsarist officers and other specialists were reincorporated into the Red army by Trotsky; others fled the country or joined the Whites.

If they were from proletariat or peasants and supporting Bolsheviks - they were... let's say, tolerated. Some of them were even praised, like Budenniy.

If they were not, even if they were supporting Bolsheviks, they had all chances to perish in waves of Great Terror.