how can I make sure only 1 instance of the function is running at any given time?

Question

I am writing a spring-boot application with @Scheduled or Shedlock which runs a function every 10 mins. That function may take varying times depending on the load, 10 min or maybe even 20 mins.

I want to make sure that the @Scheduled or Shedlock doesn't run another instance of that function while the current function is actively running. What's the best way of doing that?

I don't have a database, but I was thinking I can use DynamoDB or Redis Cache. One issue I can see is that if let's say the application crashes in the middle of the job, it will still have the cache entry. Sure, I can add a TTL to the cache entry, but then the app will still have to wait till the TTL expires.

Is there a better way to handle this situation?