Both consistency models sound similar. Both are stronger than eventual. Yet linearizability requires an ADDITIONAL guarantee that changes system design.
Linearizability
Every operation appears atomic + happens at a point between invocation + response. Real-time ordering respected.
Linearizability
Every operation appears atomic + happens at a point between invocation + response. Real-time ordering respected.
Sequential
Operations appear atomic + can be totally ordered such that each client's own program order is preserved. But wall-clock across clients isn't required.
Example difference
Alice writes X=1 at t=100ms. Bob reads at t=200ms. Linearizability: Bob MUST see X=1. Sequential: Bob may see stale X.
Cost
Linearizability requires coordination on writes — quorum, leader. Sequential can be achieved with cheaper protocols. Trade cost vs guarantee.
When you need linearizability
Locks, leader election, atomic ops. When you need sequential: many caches, session-scoped reads.