diff --git a/boltdb/translate.go b/boltdb/translate.go
index 11a92f430..40ba72cd3 100644
--- a/boltdb/translate.go
+++ b/boltdb/translate.go
@@ -27,6 +27,7 @@ import (
 	"time"
 
 	"github.com/pilosa/pilosa/v2"
+	"github.com/pilosa/pilosa/v2/topology"
 	"github.com/pkg/errors"
 	"github.com/zeebo/blake3"
 	bolt "go.etcd.io/bbolt"
@@ -626,7 +627,11 @@ func (s *TranslateStore) ComputeTranslatorSummaryCols(partitionID int, topo *pil
 	if partitionID != s.partitionID {
 		panic(fmt.Sprintf("inconsistent partitionID arg %v with TranslateStore.paritionID %v", partitionID, s.partitionID))
 	}
-	firstPrimary := topo.PrimaryNodeIndex(partitionID)
+
+	// Create a snapshot of the cluster to use for node/partition calculations.
+	snap := topology.NewClusterSnapshot(topo, topo.Hasher, topo.ReplicaN)
+
+	firstPrimary := snap.PrimaryNodeIndex(partitionID)
 
 	err = s.db.View(func(tx *bolt.Tx) error {
 
@@ -656,7 +661,7 @@ func (s *TranslateStore) ComputeTranslatorSummaryCols(partitionID int, topo *pil
 			shard := id / pilosa.ShardWidth
 
 			ks := string(v)
-			primary := topo.GetPrimaryForColKeyTranslation(s.index, ks)
+			primary := snap.PrimaryForColKeyTranslation(s.index, ks)
 			if firstPrimary < 0 {
 				firstPrimary = primary
 			} else {
@@ -666,7 +671,7 @@ func (s *TranslateStore) ComputeTranslatorSummaryCols(partitionID int, topo *pil
 			}
 
 			// Verify the invariant that the primaries agree. Just a sanity check.
-			primaryForShard := topo.GetPrimaryForShardReplication(s.index, shard)
+			primaryForShard := snap.PrimaryForShardReplication(s.index, shard)
 			if primaryForShard != firstPrimary {
 				panic(fmt.Sprintf("primaryForShard (%v) != firstPrimary (%v); key='%v', id=%v, shard=%v; partitionID=%v", primaryForShard, firstPrimary, ks, id, shard, partitionID))
 			}
@@ -1329,11 +1334,17 @@ func makeStringKeyChanges(
 		}
 	}
 
+	// Create a snapshot of the cluster to use for node/partition calculations.
+	var snap *topology.ClusterSnapshot
+	if topo != nil {
+		snap = topology.NewClusterSnapshot(topo, topo.Hasher, topo.ReplicaN)
+	}
+
 	for key2, id2 := range fwd2 {
 		//vv("makeStringKeyChanges on fwd2, key2='%v', id2=%x", key2, id2)
 		isPrimary := false
 		if topo != nil {
-			primary := topo.GetPrimaryForColKeyTranslation(s.index, key2)
+			primary := snap.PrimaryForColKeyTranslation(s.index, key2)
 			isPrimary = s.partitionID == primary
 		}
 		_ = isPrimary
diff --git a/cluster.go b/cluster.go
index b6e7e17e4..154e9f34c 100644
--- a/cluster.go
+++ b/cluster.go
@@ -899,10 +899,10 @@ func shardToShardPartition(index string, shard uint64, partitionN int) int {
 	return int(h.Sum64() % uint64(partitionN))
 }
 
-// keyPartition returns the key-partition that a key belongs to.
+// KeyPartition returns the key-partition that a key belongs to.
 // NOTE: the key-partition is DIFFERENT from the shard-partition.
-func (topo *Topology) KeyPartition(index, key string) int {
-	return keyToKeyPartition(index, key, topo.PartitionN)
+func (t *Topology) KeyPartition(index, key string) int {
+	return keyToKeyPartition(index, key, t.PartitionN)
 }
 
 func keyToKeyPartition(index, key string, partitionN int) int {
@@ -1021,31 +1021,31 @@ func (c *cluster) unprotectedPrimaryPartitionNode(partition int) *topology.Node
 	return nil
 }
 
-func (topo *Topology) IsPrimary(nodeID string, partitionID int) bool {
-	primary := topo.PrimaryNodeIndex(partitionID)
-	return nodeID == topo.nodeIDs[primary]
+func (t *Topology) IsPrimary(nodeID string, partitionID int) bool {
+	primary := t.PrimaryNodeIndex(partitionID)
+	return nodeID == t.nodeIDs[primary]
 }
 
-func (topo *Topology) PrimaryNodeIndex(partitionID int) (nodeIndex int) {
-	n := len(topo.nodeIDs)
+func (t *Topology) PrimaryNodeIndex(partitionID int) (nodeIndex int) {
+	n := len(t.nodeIDs)
 	if n == 0 {
-		if topo.cluster != nil {
-			n = len(topo.cluster.nodes)
+		if t.cluster != nil {
+			n = len(t.cluster.nodes)
 		}
 	}
-	nodeIndex = topo.Hasher.Hash(uint64(partitionID), n)
+	nodeIndex = t.Hasher.Hash(uint64(partitionID), n)
 	return
 }
 
-func (topo *Topology) GetNonPrimaryReplicas(partitionID int) (nonPrimaryReplicas []string) {
+func (t *Topology) GetNonPrimaryReplicas(partitionID int) (nonPrimaryReplicas []string) {
 
-	primary := topo.PrimaryNodeIndex(partitionID)
-	nodeN := len(topo.nodeIDs)
+	primary := t.PrimaryNodeIndex(partitionID)
+	nodeN := len(t.nodeIDs)
 
 	// Collect nodes around the ring.
 	for i := 1; i < nodeN; i++ {
-		nodeID := topo.nodeIDs[(primary+i)%nodeN]
-		if i < topo.ReplicaN {
+		nodeID := t.nodeIDs[(primary+i)%nodeN]
+		if i < t.ReplicaN {
 			nonPrimaryReplicas = append(nonPrimaryReplicas, nodeID)
 		}
 	}
@@ -1053,7 +1053,7 @@ func (topo *Topology) GetNonPrimaryReplicas(partitionID int) (nonPrimaryReplicas
 }
 
 // the map replicaNodeIDs[nodeID] will have a true value for the primary nodeID, and false for others.
-func (topo *Topology) GetReplicasForPrimary(primary int) (replicaNodeIDs, nonReplicas map[string]bool) {
+func (t *Topology) GetReplicasForPrimary(primary int) (replicaNodeIDs, nonReplicas map[string]bool) {
 	if primary < 0 {
 		// no nodes anyway
 		return
@@ -1061,12 +1061,12 @@ func (topo *Topology) GetReplicasForPrimary(primary int) (replicaNodeIDs, nonRep
 	replicaNodeIDs = make(map[string]bool)
 	nonReplicas = make(map[string]bool)
 
-	nodeN := len(topo.nodeIDs)
+	nodeN := len(t.nodeIDs)
 
 	// Collect nodes around the ring.
 	for i := 0; i < nodeN; i++ {
-		nodeID := topo.nodeIDs[(primary+i)%nodeN]
-		if i < topo.ReplicaN {
+		nodeID := t.nodeIDs[(primary+i)%nodeN]
+		if i < t.ReplicaN {
 			// mark true if primary
 			replicaNodeIDs[nodeID] = (i == 0)
 		} else {
@@ -1895,6 +1895,37 @@ func (t *Topology) String() string {
 		t.ReplicaN,
 	)
 }
+
+///////////////////////////////////////////
+// Topology implements the Noder interface.
+
+// Nodes implements the Noder interface.
+func (t *Topology) Nodes() []*topology.Node {
+	nodes := make([]*topology.Node, len(t.nodeIDs))
+	for i, nodeID := range t.nodeIDs {
+		nodes[i] = &topology.Node{
+			ID: nodeID,
+		}
+	}
+	return nodes
+}
+
+// SetNodes implements the Noder interface.
+func (t *Topology) SetNodes(nodes []*topology.Node) {}
+
+// AppendNode implements the Noder interface.
+func (t *Topology) AppendNode(node *topology.Node) {}
+
+// RemoveNode implements the Noder interface.
+func (t *Topology) RemoveNode(nodeID string) bool {
+	return false
+}
+
+// SetNodeState implements the Noder interface.
+func (t *Topology) SetNodeState(nodeID string, state string) {}
+
+///////////////////////////////////////////
+
 func (t *Topology) GetNodeIDs() []string {
 	return t.nodeIDs
 }
@@ -2609,9 +2640,9 @@ func (c *cluster) translateIndexKeys(ctx context.Context, indexName string, keys
 // are shared between replicas, and one node is the primary for
 // replication. So with 4 nodes and 3-way replication, each node has 3/4 of
 // the translation stores on it.
-func (topo *Topology) GetPrimaryForColKeyTranslation(index, key string) (primary int) {
-	partitionID := topo.KeyPartition(index, key)
-	return topo.PrimaryNodeIndex(partitionID)
+func (t *Topology) GetPrimaryForColKeyTranslation(index, key string) (primary int) {
+	partitionID := t.KeyPartition(index, key)
+	return t.PrimaryNodeIndex(partitionID)
 }
 
 // should match cluster.go:1033 cluster.ownsShard(nodeID, index, shard)
diff --git a/cmd/pilosa-fsck/fsck.go b/cmd/pilosa-fsck/fsck.go
index cef5583cd..cf6d66617 100644
--- a/cmd/pilosa-fsck/fsck.go
+++ b/cmd/pilosa-fsck/fsck.go
@@ -33,6 +33,7 @@ import (
 	"github.com/pilosa/pilosa/v2/boltdb"
 	"github.com/pilosa/pilosa/v2/internal"
 	"github.com/pilosa/pilosa/v2/server"
+	"github.com/pilosa/pilosa/v2/topology"
 	"github.com/pkg/errors"
 	"github.com/zeebo/blake3"
 )
@@ -782,6 +783,9 @@ func (cfg *FsckConfig) analyzeThisIndex(
 			index, len(nodes2fragsum), nodes2fragsum)
 	}
 
+	// Create a snapshot of the cluster to use for node/partition calculations.
+	snap := topology.NewClusterSnapshot(cfg.topo, cfg.topo.Hasher, cfg.topo.ReplicaN)
+
 	for node, sum := range nodes2fragsum {
 		if !quiet {
 			fmt.Printf("# on node '%v'\n", node)
@@ -798,7 +802,7 @@ func (cfg *FsckConfig) analyzeThisIndex(
 			totalFiles++
 			//vv("checking %v on node %v", relpath, node)
 
-			replicas, nonReplicas := cfg.topo.GetReplicasForPrimary(fragsum.Primary)
+			replicas, nonReplicas := snap.ReplicasForPrimary(fragsum.Primary)
 			_, _ = replicas, nonReplicas
 			//vv("replicas = '%#v'", replicas)
 			//vv("nonReplicas = '%#v'", nonReplicas)
diff --git a/fragment.go b/fragment.go
index 20cdcf380..d87171807 100644
--- a/fragment.go
+++ b/fragment.go
@@ -3555,8 +3555,12 @@ func (s *fragmentSyncer) syncFragment() error {
 	span, ctx := tracing.StartSpanFromContext(context.Background(), "FragmentSyncer.syncFragment")
 	defer span.Finish()
 
+	// Create a snapshot of the cluster to use for node/partition calculations.
+	// TODO: this needs to use Cluster.noder once that has been implemented.
+	snap := topology.NewClusterSnapshot(topology.NewLocalNoder(s.Cluster.Nodes()), s.Cluster.Hasher, s.Cluster.ReplicaN)
+
 	// Determine replica set.
-	nodes := s.Cluster.shardNodes(s.Fragment.index(), s.Fragment.shard)
+	nodes := snap.ShardNodes(s.Fragment.index(), s.Fragment.shard)
 	if len(nodes) == 1 {
 		return nil
 	}
@@ -3672,9 +3676,13 @@ func (s *fragmentSyncer) syncBlockFromPrimary(id int) error {
 
 	f := s.Fragment
 
+	// Create a snapshot of the cluster to use for node/partition calculations.
+	// TODO: this needs to use Cluster.noder once that has been implemented.
+	snap := topology.NewClusterSnapshot(topology.NewLocalNoder(s.Cluster.Nodes()), s.Cluster.Hasher, s.Cluster.ReplicaN)
+
 	// Determine replica set. Return early if this is not
 	// the primary node.
-	nodes := s.Cluster.shardNodes(f.index(), f.shard)
+	nodes := snap.ShardNodes(f.index(), f.shard)
 	if s.Node.ID != nodes[0].ID {
 		f.holder.Logger.Debugf("non-primary replica expecting sync from primary: %s, index=%s, field=%s, shard=%d", nodes[0].ID, f.index(), f.field(), f.shard)
 		return nil
@@ -3721,10 +3729,14 @@ func (s *fragmentSyncer) syncBlock(id int) error {
 
 	f := s.Fragment
 
+	// Create a snapshot of the cluster to use for node/partition calculations.
+	// TODO: this needs to use Cluster.noder once that has been implemented.
+	snap := topology.NewClusterSnapshot(topology.NewLocalNoder(s.Cluster.Nodes()), s.Cluster.Hasher, s.Cluster.ReplicaN)
+
 	// Read pairs from each remote block.
 	var uris []*pnet.URI
 	var pairSets []pairSet
-	for _, node := range s.Cluster.shardNodes(f.index(), f.shard) {
+	for _, node := range snap.ShardNodes(f.index(), f.shard) {
 		if s.Node.ID == node.ID {
 			continue
 		}
diff --git a/index.go b/index.go
index 6129289f5..457869d6a 100644
--- a/index.go
+++ b/index.go
@@ -32,6 +32,7 @@ import (
 	"github.com/pilosa/pilosa/v2/roaring"
 	"github.com/pilosa/pilosa/v2/stats"
 	"github.com/pilosa/pilosa/v2/testhook"
+	"github.com/pilosa/pilosa/v2/topology"
 	"github.com/pkg/errors"
 	"github.com/zeebo/blake3"
 	"golang.org/x/sync/errgroup"
@@ -847,6 +848,9 @@ floop:
 		fmt.Printf("# ====================\n")
 	}
 
+	// Create a snapshot of the cluster to use for node/partition calculations.
+	snap := topology.NewClusterSnapshot(topo, topo.Hasher, topo.ReplicaN)
+
 tloop:
 	for partitionID, store := range idx.translateStores {
 		partitionID := partitionID
@@ -855,7 +859,7 @@ tloop:
 		fun2 := func(worker int) error {
 			//vv("ComputeTranslatorSummary() running on store.Path = '%v'", store.GetStorePath())
 			if checkKeys {
-				prim := topo.PrimaryNodeIndex(partitionID)
+				prim := snap.PrimaryNodeIndex(partitionID)
 				primID := topo.nodeIDs[prim]
 
 				// note: we fix irrespective of nodeID == primID now, so that we
@@ -891,9 +895,9 @@ tloop:
 			sum.Index = idx.Name()
 			sum.StorePath = store.GetStorePath()
 			sum.NodeID = nodeID
-			sum.IsPrimary = topo.IsPrimary(nodeID, partitionID)
+			sum.IsPrimary = snap.IsPrimary(nodeID, partitionID)
 
-			replicas := topo.GetNonPrimaryReplicas(partitionID)
+			replicas := snap.NonPrimaryReplicas(partitionID)
 			for _, replica := range replicas {
 				if nodeID == replica {
 					sum.IsReplica = true
@@ -980,6 +984,10 @@ func (idx *Index) WriteFragmentChecksums(w io.Writer, showBits, showOps bool, to
 		IndexPath:    idx.path,
 		RelPath2fsum: make(map[string]*FragSum),
 	}
+
+	// Create a snapshot of the cluster to use for node/partition calculations.
+	snap := topology.NewClusterSnapshot(topo, topo.Hasher, topo.ReplicaN)
+
 	paths, err := listFilesUnderDir(idx.path, false, "", true)
 	panicOn(err)
 	index := idx.name
@@ -990,7 +998,7 @@ func (idx *Index) WriteFragmentChecksums(w io.Writer, showBits, showOps bool, to
 			continue // ignore .meta paths
 		}
 		abspath := idx.path + sep + relpath
-		primary := topo.GetPrimaryForShardReplication(index, shard)
+		primary := snap.PrimaryForShardReplication(index, shard)
 
 		checksum, hotbits := RoaringFragmentChecksum(abspath, index, field, view, shard)
 		if verbose {