Caustic sinks work differently to the heatsinks, just in case you are not aware. They have a bar which fills up over time (or per hit if struck by caustic missiles) and only requires ejection when filled/near full to continue working. They can take I think two Cyclops missiles with third overtopping, one from a Basilisk while the second applies light caustic (light enough to be negligible), and you'll want to avoid Medusa and Hydra salvos regardless. Medusa missiles fill it by maybe, idk, 75-80%? Not quite sure. Hydra missile is basically 99% filled in one hit, and both of them launch volleys of three.
The sink can take a good few Scout and Glaive missiles before it requires ejection, as they are individually weaker. If the caustic sink looks like it's frozen, they require a second or two to eject unlike heatsinks which activate and remain so over a period of time when triggered, before auto-ejecting.
(There might also be periodic Titans in the future, depending on where Frontier take all of this content after it has passed its initial, two-year highlight. We're all kind of just guessing how it will, but it's likely that this stuff and its assets will be kept around and in use.)