[{"network_type":"ex","rack":[{"xxxx":{"asn":111111,"nodes":{"business":["tt550abcc1eb01"],"master":["tt550abcc1eb02"]},"region":"ex-01","zone":"01a"},"yyyy":{"asn":22222,"nodes":{"business":["er44abcc1eb28"]},"region":"ex-02","zone":"02a"}}]}]

db.collection.find({"rack.$[].nodes.$[]":"er44abcc1eb28"},{})