How to design and develop stateful microservices for scale and resiliency?

I want to develop a microservice (preferably using Spring!) that monitors a requested directory on FTP server. The input params for the service are - ftp server, credentials for connection and directory path to be monitored.

The service could receive multiple requests and will be monitoring the requested assets for changes.

The questions are -

1. For scalability, there might be multiple instances of this service running and sharing the load among them. Each service instance will have its own state [assets under active monitoring]. If any of the service instances fail, how to transfer the state to another instance?

2. How to make this service resilient? If all service instances fail, how to re-launch the service with the last known state?

Thanks in advance, Nirav