diff --git a/go.mod b/go.mod
index 9cb82fbc..808b2e7a 100644
--- a/go.mod
+++ b/go.mod
@@ -109,6 +109,7 @@ require (
 	github.com/urfave/cli/v2 v2.27.7 // indirect
 	github.com/urfave/cli/v3 v3.6.1 // indirect
 	github.com/xrash/smetrics v0.0.0-20250705151800-55b8f293f342 // indirect
+	github.com/xtgo/set v1.0.0 // indirect
 	go.yaml.in/yaml/v2 v2.4.3 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
 	golang.org/x/exp v0.0.0-20250620022241-b7579e27df2b // indirect
diff --git a/go.sum b/go.sum
index 8d3904ae..39571309 100644
--- a/go.sum
+++ b/go.sum
@@ -318,6 +318,8 @@ github.com/vektah/gqlparser/v2 v2.5.31 h1:YhWGA1mfTjID7qJhd1+Vxhpk5HTgydrGU9IgkW
 github.com/vektah/gqlparser/v2 v2.5.31/go.mod h1:c1I28gSOVNzlfc4WuDlqU7voQnsqI6OG2amkBAFmgts=
 github.com/xrash/smetrics v0.0.0-20250705151800-55b8f293f342 h1:FnBeRrxr7OU4VvAzt5X7s6266i6cSVkkFPS0TuXWbIg=
 github.com/xrash/smetrics v0.0.0-20250705151800-55b8f293f342/go.mod h1:Ohn+xnUBiLI6FVj/9LpzZWtj1/D6lUovWYBkxHVV3aM=
+github.com/xtgo/set v1.0.0 h1:6BCNBRv3ORNDQ7fyoJXRv+tstJz3m1JVFQErfeZz2pY=
+github.com/xtgo/set v1.0.0/go.mod h1:d3NHzGzSa0NmB2NhFyECA+QdRp29oEn2xbT+TpeFoM8=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
 go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
diff --git a/internal/repository/job.go b/internal/repository/job.go
index 99970ce1..1ff8047e 100644
--- a/internal/repository/job.go
+++ b/internal/repository/job.go
@@ -76,6 +76,7 @@ import (
 	"github.com/ClusterCockpit/cc-lib/v2/schema"
 	sq "github.com/Masterminds/squirrel"
 	"github.com/jmoiron/sqlx"
+	"github.com/xtgo/set"
 )
 
 var (
@@ -772,3 +773,63 @@ func (r *JobRepository) UpdateFootprint(
 
 	return stmt.Set("footprint", string(rawFootprint)), nil
 }
+
+func (r *JobRepository) GetUsedNodes(ts uint64) map[string][]string {
+	q := sq.Select("job.cluster", "job.resources").From("job").
+		Where("job.start_time < ?", ts).
+		Where(sq.Eq{"job.job_state": "running"})
+
+	rows, err := q.RunWith(r.stmtCache).Query()
+	if err != nil {
+		queryString, queryVars, _ := q.ToSql()
+		cclog.Errorf("Error while running query '%s' %v: %v", queryString, queryVars, err)
+		return nil
+	}
+	defer rows.Close()
+
+	// Use a map of sets for efficient deduplication
+	nodeSet := make(map[string]map[string]struct{})
+
+	var (
+		cluster      string
+		rawResources []byte
+		resources    []*schema.Resource
+	)
+
+	for rows.Next() {
+		if err := rows.Scan(&cluster, &rawResources); err != nil {
+			cclog.Warnf("Error scanning job row in GetUsedNodes: %v", err)
+			continue
+		}
+
+		if err := json.Unmarshal(rawResources, &resources); err != nil {
+			cclog.Warnf("Error unmarshaling resources for cluster %s: %v", cluster, err)
+			continue
+		}
+
+		if _, ok := nodeSet[cluster]; !ok {
+			nodeSet[cluster] = make(map[string]struct{})
+		}
+
+		for _, res := range resources {
+			nodeSet[cluster][res.Hostname] = struct{}{}
+		}
+	}
+
+	if err := rows.Err(); err != nil {
+		cclog.Errorf("Error iterating rows in GetUsedNodes: %v", err)
+	}
+
+	nodeList := make(map[string][]string)
+	for cluster, nodes := range nodeSet {
+		// Convert map keys to slice
+		list := make([]string, 0, len(nodes))
+		for node := range nodes {
+			list = append(list, node)
+		}
+		// set.Strings sorts the slice and ensures uniqueness
+		nodeList[cluster] = set.Strings(list)
+	}
+
+	return nodeList
+}