CAP Theorem
Brewer's Theorem
The CAP theorem says a distributed data store can only give you two out of three of these during a network partition. Consistency means every read sees the...
Plain English definitions for the engineering ideas you keep running into.
No terms match your search. Try a different keyword.
Brewer's Theorem
The CAP theorem says a distributed data store can only give you two out of three of these during a network partition. Consistency means every read sees the...
Distributed Consensus, Agreement Protocol
Consensus is a way for a group of computers to agree on the same value, even if some of them are slow, crashed, or cut off from the...
Liveness Probe, Keep Alive
A heartbeat is a small message a node sends every so often to say it is still alive. If the heartbeats stop, other nodes assume it has failed...
HWM, Commit Index
The high watermark is the largest log offset that has been copied to a quorum of replicas. Anything at or below this point is committed and safe to...
HLC, Hybrid Time
A hybrid logical clock, or HLC, is a clock that mixes the wall clock time with a small counter. The result is a 64 bit number that always...
Master Election, Coordinator Election
Leader election is how a group of nodes picks one node to coordinate writes, order operations, or own a shard. The winner stays leader for some time. If...
Time Bound Lease, Lock with TTL
A lease is a grant that gives one node exclusive access to a resource for a fixed amount of time, called the TTL. The holder has to keep...
Raft Consensus Algorithm
Raft is a consensus algorithm from 2014 that gives the same fault tolerance as Paxos but is much easier to read and write. It splits the problem into...
Distributed Log, Append Only Log
A replicated log is a list of operations that is kept in the same order on many machines using a consensus protocol. Every node applies the entries in...
Time To Live, Expiry
TTL stands for time to live. It is a length of time after which something like a lease, a cache entry, a DNS record, or a token is...
2PC, XA Transactions
Two phase commit, or 2PC, is a protocol for committing a transaction across many resources at once. A coordinator first asks every participant if they can commit. If...