From the code below, identify the implicit dependency:
1. resource "aws_eip" "public_ip" {
2. vpc = true
3. instance = aws_instance.web_server.id
4. }
5. resource "aws_instance" "web_server" {
6. ami = "ami-2757f631"
7. instance_type = "t2.micro"
8. depends_on = [aws_s3_bucket.company_data]
9. }
When configuring Vault replication and monitoring its status, you keep seeing something called 'WALs'. What are WALs?