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Live Shard Rebalancing Service · Brief · designlab

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Library ArchitectureLive Shard Rebalancing Service

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Live Shard Rebalancing Service

HLDAdvanced60 minStorage & partitioning Coordination & scheduling Reliability & recovery

All changes saved Not started

01 · Understand the problem

Your mission

Move one bounded key range from a source shard to a destination without changing its data schema. Storage supports consistent snapshot/log pairing and versioned writes. Routers can be stale, so shard servers must enforce ownership.

02 · Define success

Requirements

Keep one writable authority for the moving range.
Copy a snapshot and replay updates without gaps.
Fence the old owner before publishing the new directory epoch.
Retain enough source history for retries and operational recovery.

Open the design canvas Read the analysis first

Design envelope

35,000
peak reads / s: 12,000
writes / s: 200 ms
target read p99: 1800 B
record size

Workload assumptions for this exercise, not measured production limits.

Think about request flow, durable state, hot paths and failure boundaries.

How this problem works

Design — place components and connect them on the canvas, then write your contracts.
Decide — pick the policies you would defend and note the trade-offs.
Review — run the rule-based review. Pass every check to complete the problem and add it to your review deck.

The review checks a guided model. Other valid architectures exist; it does not execute code or prove production readiness.