This article explains an example of commit check failed with error "cannot add route to db".

On MX routers with Junos OS 15.1 or higher, the following errors may appear when executing commit or commit check:

user@MX1# commit check
error:  cannot add route to db
error: configuration check-out failed

In this case, the error is relevant to the dcd (interface control process):

# commit check | display detail
...
2019-06-12 08:47:46 IST: Collecting status of Interface control process
error:  cannot add route to db
...

Two or more interfaces may be configured with the same address, and at least one of the interfaces is configured with a static ARP entry.

Example of problem configuration:

interfaces {
    ge-0/0/0 {
        unit 0 {
            family inet {
                address 10.0.0.1/24;
            }
        }
    }
    ge-0/0/1 {
        unit 0 {
            family inet {
                address 10.0.0.1/24 {
                    arp 10.0.0.2 mac 00:00:01:00:00:01;
                }
            }
        }
    }
}

Correct the duplicate IP address.