Definition
An extension of CAP: if Partitioned, choose Availability or Consistency; Else, choose Latency or Consistency.
How it works
CAP only describes behaviour during a partition. PACELC adds the common case: even with a healthy network, stronger consistency costs latency (you must coordinate replicas). Spanner is PC/EC (consistency always); Dynamo/Cassandra are PA/EL (availability + low latency, eventual consistency).
Common questions
What is PACELC?
An extension of CAP: if Partitioned, choose Availability or Consistency; Else, choose Latency or Consistency.
How does PACELC work?
CAP only describes behaviour during a partition. PACELC adds the common case: even with a healthy network, stronger consistency costs latency (you must coordinate replicas). Spanner is PC/EC (consistency always); Dynamo/Cassandra are PA/EL (availability + low latency, eventual…
What is PACELC used for in system design?
CAP only describes behaviour during a partition. PACELC adds the common case: even with a healthy network, stronger consistency costs latency (you must coordinate replicas). Spanner is PC/EC (consistency always); Dynamo/Cassandra are PA/EL (availability + low latency, eventual…