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Eventual Consistency

A common consistency model in NoSQL, where data updates may not be immediately reflected across all replicas, prioritizing availability.
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The statement of the theorem

Consider a distributed system with NN replicas, R={r1,…,rN}\mathcal{R} = \{r_1, \dots, r_N\}, and a state variable SS. Let St(ri)S_t(r_i) be the state of replica rir_i at time tt. The system is eventually consistent if, for any write operation WW applied at time t0t_0, the state St(ri)S_{t}(r_i) converges to the final state S∞S_{\infty} for all ri∈Rr_i \in \mathcal{R} as t→∞t \to \infty. Formally, there exists a time TT such that for all t≥Tt \ge T and all ri,rj∈Rr_i, r_j \in \mathcal{R}, St(ri)=St(rj)=S∞S_t(r_i) = S_t(r_j) = S_{\infty}. This convergence is guaranteed despite potential network partitions.
Source: Wikipedia