--- title: Valkey · Resharding, Reimagined: Introducing Atomic Slot... description: Valkey 9.0 introduces Atomic Slot Migration, a rework of cluster resharding that replaces the legacy per-key MIGRATE-based process with a replication-style... canonical: https://daily.dev/posts/valkey-resharding-reimagined-introducing-atomic-slot-migration-jw1biiwok twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Valkey · Resharding, Reimagined: Introducing Atomic Slot Migration | daily.dev og:description: Valkey 9.0 introduces Atomic Slot Migration, a rework of cluster resharding that replaces the legacy per-key MIGRATE-based process with a replication-style... og:url: https://daily.dev/posts/valkey-resharding-reimagined-introducing-atomic-slot-migration-jw1biiwok og:image: https://api.daily.dev/og/posts/JW1BIIwOK.png og:image:alt: Valkey · Resharding, Reimagined: Introducing Atomic Slot Migration og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Valkey · Resharding, Reimagined: Introducing Atomic Slot Migration **[Valkey](https://daily.dev/sources/valkey-blog)** · 10 min read · 0 upvotes · 0 comments ## Summary Valkey 9.0 introduces Atomic Slot Migration, a rework of cluster resharding that replaces the legacy per-key MIGRATE-based process with a replication-style handover. Data is snapshotted and streamed asynchronously to the target node, then ownership is atomically transferred once the target is caught up. This eliminates ASK redirections, removes multi-key operation failures during migration, handles large keys via chunked replay instead of single large commands, supports cancellation with automatic rollback, and delivers up to 9x faster migrations with far less client-visible impact. New CLUSTER commands (MIGRATESLOTS, CANCELSLOTMIGRATIONS, GETSLOTMIGRATIONS) and an internal CLUSTER SYNCSLOTS state machine drive the new lifecycle. Benchmarks on GCE VMs show migration times dropping from over a minute to roughly 10 seconds under no load, and from over two minutes to about 30 seconds under heavy read/write load. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What is Atomic Slot Migration in Valkey 9.0 and how does it differ from the legacy slot migration process? Atomic Slot Migration is a new resharding mechanism in Valkey 9.0 that replicates slot contents from source to target node in three phases (snapshot, streaming, finalization) and atomically transfers ownership once the target is caught up. Unlike legacy migration, which moved keys one at a time via CLUSTER GETKEYSINSLOT and MIGRATE with ASK redirections, clients remain unaware of the migration entirely, and large collections are replayed as chunked commands instead of single large payloads. _Teams planning a Valkey cluster resharding can follow migration changes like this on daily.dev._ ### How much faster is Valkey 9.0's atomic slot migration compared to legacy slot migration? In benchmarks on GCE c4-standard-8 VMs with 40GB of 16KB string keys, atomic slot migration was up to 9.52x faster under no load (10.7s vs 1m42s for a 3-to-4 shard scale-out) and 4.62-4.75x faster under heavy read/write load using memtier-benchmark with a 1:10 set/get ratio. The main cause of legacy slowness was hundreds of thousands of network round trips for GETKEYSINSLOT and MIGRATE commands. _Engineers benchmarking database scaling strategies can track results like these on daily.dev._ ### What new CLUSTER commands does Valkey 9.0 provide for managing slot migrations? Valkey 9.0 adds CLUSTER MIGRATESLOTS SLOTSRANGE start-slot end-slot NODE node-id to start a migration across one or more slot ranges, CLUSTER CANCELSLOTMIGRATIONS to safely cancel all ongoing migrations from a node, and CLUSTER GETSLOTMIGRATIONS to view an observable log of recent and active migration jobs stored in memory, including status, duration, and outcome. _Operators adopting new cluster commands can follow Valkey's evolving tooling on daily.dev._ ## Similar posts on daily.dev - [Valkey 9.0 Introduces Multi-Database Clustering, Atomic Slot Migration, and Major Performance Gains](https://daily.dev/posts/valkey-9-0-introduces-multi-database-clustering-atomic-slot-migration-and-major-performance-gains-2gkxrlley) · InfoQ · 7 upvotes · 0 comments - [Valkey 9.0 Debuts Multidatabase Clustering for Massive-Scale Workloads](https://daily.dev/posts/valkey-9-0-debuts-multidatabase-clustering-for-massive-scale-workloads-bmxbj7zgl) · The New Stack · 14 upvotes · 0 comments - [Valkey · Analyzing Atomic Slot Migration ACL requirements](https://daily.dev/posts/valkey-analyzing-atomic-slot-migration-acl-requirements-c2hg69ftb) · Valkey · 4 upvotes · 0 comments - [Announcing Valkey 9.1 for Amazon ElastiCache](https://daily.dev/posts/announcing-valkey-9-1-for-amazon-elasticache-pvemznhnh) · AWS Database Blog · 0 upvotes · 0 comments --- Tags: [#database](https://daily.dev/tags/database), [#distributed-systems](https://daily.dev/tags/distributed-systems), [#redis](https://daily.dev/tags/redis), [#valkey](https://daily.dev/tags/valkey) [View this post on daily.dev](https://daily.dev/posts/valkey-resharding-reimagined-introducing-atomic-slot-migration-jw1biiwok) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Valkey · Resharding, Reimagined: Introducing Atomic Slot Migration","url":"https://daily.dev/posts/valkey-resharding-reimagined-introducing-atomic-slot-migration-jw1biiwok","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/valkey-resharding-reimagined-introducing-atomic-slot-migration-jw1biiwok"},"datePublished":"2026-08-23T12:23:18.750Z","dateModified":"2026-08-23T12:54:14.491Z","description":"Valkey 9.0 introduces Atomic Slot Migration, a rework of cluster resharding that replaces the legacy per-key MIGRATE-based process with a replication-style...","image":"https://media.daily.dev/image/upload/s--1KxV4ohY--/f_auto/v1722860400/public/Placeholder%2007","thumbnailUrl":"https://media.daily.dev/image/upload/s--1KxV4ohY--/f_auto/v1722860400/public/Placeholder%2007","isAccessibleForFree":true,"articleSection":"Valkey","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Valkey","logo":"https://media.daily.dev/image/upload/s--XXPzEmD8--/f_auto,q_auto/v1787487496/logos/valkey-blog?_a=BAMAMicg0","url":"https://daily.dev/sources/valkey-blog"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/valkey-resharding-reimagined-introducing-atomic-slot-migration-jw1biiwok","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"database,distributed-systems,redis,valkey","timeRequired":"PT10M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Valkey","item":"https://daily.dev/sources/valkey-blog"},{"@type":"ListItem","position":3,"name":"Valkey · Resharding, Reimagined: Introducing Atomic Slot Migration"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/valkey-resharding-reimagined-introducing-atomic-slot-migration-jw1biiwok#faq","mainEntity":[{"@type":"Question","name":"What is Atomic Slot Migration in Valkey 9.0 and how does it differ from the legacy slot migration process?","acceptedAnswer":{"@type":"Answer","text":"Atomic Slot Migration is a new resharding mechanism in Valkey 9.0 that replicates slot contents from source to target node in three phases (snapshot, streaming, finalization) and atomically transfers ownership once the target is caught up. 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