A replica set yaiku grup saka MongoDB servers kang nglestarekake data kang padha — nyedhiyakake high availability (automatic failover) lan redundancy. Siji node yaiku primary (nangani writes), liyane yaiku secondaries (nggandakake data saka primary lan bisa nglayang reads). Iki mekanisme standar MongoDB kanggo reliability.
Struktur replica set
PRIMARY (1) → receives all WRITES; replicates changes to secondaries
SECONDARIES (2+) → copy the primary's data (via the oplog); can serve READS
ARBITER (optional) → votes in elections but holds no data (for odd vote counts)
Write → Primary → replicated to Secondaries (via the operations log "oplog")
