Top 4 Replication Interview Questions
Browse 4 real-world technical and behavioral interview questions about Replication. Review scenarios, edge cases, and architectural best practices.
Two teams need the same customer data. Do you give them one shared database, or two copies that are allowed to disagree?
Name the single writer first, then choose which coupling you would rather own: a shared schema couples the two teams' release calendars, while a replicated copy couples them to a staleness window and obliges someone to detect and repair divergence. Both are permanent, so pick the one your organisation can pay for.
Photos are the payload, thumbnails are the traffic, and both must survive losing a disk. Where does each copy live?
Photo storage should separate originals from thumbnails. Originals are large, rarely read and irreplaceable, so keep a canonical erasure-coded object; thumbnails are small, hot and rebuildable, so replicate them, cache them at the edge and address them by content or transform version.
CAP says you must choose between consistency and availability under a network partition. What are you giving up, concretely?
Under partition you either reject requests on the side that cannot reach a quorum, or serve them and accept divergent replicas that need reconciling. CAP's C is linearisability, not ACID's C, and the choice binds only while partitioned.
Your service writes a record, reads it straight back, and sometimes gets the old value. What is happening and what do you change?
An acknowledged write is only guaranteed on the replicas that acknowledged it, so a read served elsewhere can legitimately return the previous version. Locate the staleness - replica, secondary index or cache - then buy read-your-writes for that operation only, and price what it costs during a partition.