Hybrid core transition through plateaus

The decision

Design plateaus that allow cloud capabilities to coexist with on-premise cores and evolve in a controlled manner toward the target cloud core.

Why it mattered

The target cloud core is not available as an immediate replacement, and the bank cannot stop operations for a big-bang substitution.

The trade-off

Temporary coexistence increases integration and operational complexity, but reduces transformation risk and decouples capability modernization from the core-replacement schedule.

What changed

The target no longer depended on a single AS-IS → TO-BE jump and was expressed as a governable sequence of states.

The outcome

Implementation is not claimed; architecture and transformation design remain in progress.

Summary of a documented architecture decision. Method, mechanism and supporting evidence are not published.