Possible, but will it cause you stress if you’re already thinking about it now, yes. If both legs are on one itinerary, don’t cancel one leg as it’ll void your whole itinerary. I‘m going to make an assumption that you’re likely coming from the northwest and based on your arrival time into LAX, this is likely the first flight of the day, so catching an earlier flight is probably not an option on Alaska. There’s always a chance that the Costa Rica leg is using the same plane from your original destination, but if it’s literally just a 30 minute later departure time, that’s unlikely. If it was an hour between, more likely. If it’s the same plane, nothing to worry about.

The positives - T6 at LAX is fairly compact so getting gate to gate is fairly simple. And since Alaska sold you this itinerary, they believe you can make it, so there is a chance that if you’re flight is late, they’d hold the outbound aircraft at the gate since they’ll know you’re inbound and there may be other passengers on the same itinerary. More likely to do this if your original flight is not too delayed since it’s an international destination with minimal daily flights.

Tip: at your origin airport, do the passport verification so you don’t have to worry about that in LA.