redis-clustering
Redis Cluster and replication guidance covering hash tags for multi-key operations, avoiding CROSSSLOT errors, and reading from replicas to scale read-heavy workloads. Use when designing keys for a sharded Redis Cluster, debugging CROSSSLOT errors on MGET / SDIFF / pipelines, configuring a multi-key transaction in a cluster, or routing reads to replicas for caches, analytics, or dashboards.
- Installs
- 1.8K
- Last 24h
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- #7036
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/redis/agent-skills --skill redis-clustering- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads redis-clustering automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
Redis Clustering
Guidance for designing keys and routing reads in a sharded Redis Cluster (and in standalone primary/replica replication). Covers the two failure modes that bite most new cluster users: CROSSSLOT errors on multi-key operations, and overloading primaries with read traffic.
When to apply
- Designing keys for a Redis Cluster deployment.
- Debugging a
CROSSSLOTerror onMGET,SDIFF, transactions, or pipelines. - Implementing transactions / Lua scripts that touch multiple keys.
- Scaling out read traffic without adding shards.
1. Hash tags for multi-key operations
Redis Cluster distributes keys across 16,384 slots by hashing the key name. Any command that touches multiple keys (MGET, SDIFF, SUNIONSTORE, transactions, pipelines, Lua scripts with multiple KEYS[]) requires all keys to live on the same slot — otherwise the server returns a CROSSSLOT error.
Hash tags force this: the part between { and } is the only thing hashed for slot assignment, so two keys sharing a hash tag always land together.
# Same slot — multi-key ops work
redis.set("{user:1001}:profile", "...")
redis.set("{user:1001}:settings", "...")
redis.lmove("{user:1001}:pending", "{user:1001}:processed", "LEFT", "RIGHT")
# Different keys, no hash tag — CROSSSLOT on multi-key commands in cluster mode
redis.set("user:1001:profile", "...")
redis.set("user:1001:settings", "...")
pipe = redis.pipeline()
pipe.get("user:1001:profile")
pipe.get("user:1001:settings")
pipe.execute() # CROSSSLOT error in cluster
Rules of thumb:
- Use a tag scoped to the meaningful entity, e.g.
{user:1001}. Avoid bare{1001}— unrelated namespaces (purchase:{1001},employee:{1001}) would all collide on the same slot. - Only tag where you actually need multi-key ops. Tagging everything creates hotspots and defeats the point of sharding.
- A single-key command on a hash-tagged key works fine, so adding tags later is incremental — but renaming keys in production is painful, so plan tagging up front for entities you'll group.
See references/hash-tags.md.
2. Read replicas for read-heavy workloads
If reads dominate writes, route them to replicas to free primary capacity. Works both in Redis Cluster (each shard has 1+ replica) and in standalone primary/replica replication.
# Redis Cluster: enable replica reads on the client
from redis.cluster import RedisCluster
rc = RedisCluster(host="localhost", port=6379, read_from_replicas=True)
rc.set("key", "value") # → primary
value = rc.get("key") # → may be served by a replica
For non-cluster setups, point two clients at the right nodes:
primary = Redis(host="primary-host", port=6379)
replica = Redis(host="replica-host", port=6379)
primary.set("key", "value")
value = replica.get("key")
The trade-off is consistency: replicas are eventually consistent. Don't read your own writes from a replica; don't use replica reads for anything that requires strict freshness (financial balances, idempotency state). Good fits: cache layers, analytics, dashboards, recommendation feeds.
See references/read-replicas.md.
References
FAQ
What does the redis-clustering skill do?
Redis Cluster and replication guidance covering hash tags for multi-key operations, avoiding CROSSSLOT errors, and reading from replicas to scale read-heavy workloads. Use when designing keys for a sharded Redis Cluster, debugging CROSSSLOT errors on MGET / SDIFF / pipelines, configuring a multi-key transaction in a cluster, or routing reads to replicas for caches, analytics, or dashboards.
How do I install redis-clustering?
Run npx skills add https://github.com/redis/agent-skills --skill redis-clustering in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/redis-clustering/ (personal) or .claude/skills/redis-clustering/ (project).
Which AI agents can use redis-clustering?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is redis-clustering safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains redis-clustering?
It is published by redis in redis/agent-skills, and it is an official skill from the maker of the technology it covers. It has 1,826 recorded installs.
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