Miroir

Multi-node Index Replication Orchestrator, Integrated Rebalancing

Miroir is a RAID-like orchestration layer for Meilisearch. It stripes a large index across a fleet of small-RAM Meilisearch nodes with a configurable replication factor, fans out search queries across all shards, and rebalances shard assignments when nodes are added or removed — all using the Meilisearch Community Edition.

The Problem

Meilisearch loads its entire index into memory-mapped LMDB files. A large index that exceeds a single server's available RAM cannot run on that server. The Enterprise Edition's native sharding is gated behind a commercial license. Miroir solves this without it.

How It Works

Client
  │
  ▼
Miroir Orchestrator
  ├── Write path: hash(doc_id) → assign to shard → write to R replicas
  ├── Read path:  scatter query to all shards → gather → merge ranked results
  └── Rebalance: on node add/remove → recompute assignments → migrate minimum shards

Meilisearch Nodes (N instances, each holding a subset of shards)
  node-0   node-1   node-2   ...   node-N

Replication Factor

Analogous to software RAID — configurable per deployment:

RF	Redundancy	Node failures tolerated	Capacity
1	None (stripe only)	0	100% of fleet
2	One replica	1 per shard group	50% of fleet
3	Two replicas	2 per shard group	33% of fleet

Key Components

• Orchestrator — proxy that handles shard routing, scatter-gather, result merging, and topology management
• Shard router — consistent hash function (Rendezvous/HRW) mapping document IDs to node assignments; minimal reshuffling on topology change
• Rebalancer — on node add/remove, recomputes assignments and migrates only the shards that changed owners; surviving replicas serve reads during rebuild
• Result merger — normalizes and merges ranked result sets from multiple shards into a single coherent response

Status

Design phase. See docs/ for architecture detail.