diff --git a/persist/sqlite/init.sql b/persist/sqlite/init.sql
index 0d55dd6c..7cd147ec 100644
--- a/persist/sqlite/init.sql
+++ b/persist/sqlite/init.sql
@@ -47,7 +47,7 @@ CREATE TABLE storage_volumes (
 	read_only BOOLEAN NOT NULL,
 	available BOOLEAN NOT NULL DEFAULT false
 );
-CREATE INDEX storage_volumes_read_only_available ON storage_volumes(read_only, available);
+CREATE INDEX storage_volumes_id_available_read_only ON storage_volumes(id, available, read_only);
 CREATE INDEX storage_volumes_read_only_available_used_sectors ON storage_volumes(available, read_only, used_sectors);
 
 CREATE TABLE volume_sectors (
@@ -57,6 +57,7 @@ CREATE TABLE volume_sectors (
 	sector_id INTEGER UNIQUE REFERENCES stored_sectors (id),
 	UNIQUE (volume_id, volume_index)
 );
+CREATE INDEX volume_sectors_volume_id_sector_id_volume_index_compound ON volume_sectors(volume_id, sector_id, volume_index) WHERE sector_id IS NULL;
 CREATE INDEX volume_sectors_volume_id_sector_id ON volume_sectors(volume_id, sector_id);
 CREATE INDEX volume_sectors_volume_id ON volume_sectors(volume_id);
 CREATE INDEX volume_sectors_volume_index ON volume_sectors(volume_index ASC);
diff --git a/persist/sqlite/migrations.go b/persist/sqlite/migrations.go
index 62587e09..bea64182 100644
--- a/persist/sqlite/migrations.go
+++ b/persist/sqlite/migrations.go
@@ -9,6 +9,17 @@ import (
 	"go.sia.tech/hostd/host/contracts"
 )
 
+// migrateVersion19 adds a compound index to the volume_sectors table
+func migrateVersion19(tx txn) error {
+	const query = `
+DROP INDEX storage_volumes_read_only_available;
+CREATE INDEX storage_volumes_id_available_read_only ON storage_volumes(id, available, read_only);
+CREATE INDEX volume_sectors_volume_id_sector_id_volume_index_compound ON volume_sectors(volume_id, sector_id, volume_index) WHERE sector_id IS NULL;
+`
+	_, err := tx.Exec(query)
+	return err
+}
+
 // migrateVersion18 adds an index to the volume_sectors table to speed up
 // empty sector selection.
 func migrateVersion18(tx txn) error {
@@ -493,4 +504,5 @@ var migrations = []func(tx txn) error{
 	migrateVersion16,
 	migrateVersion17,
 	migrateVersion18,
+	migrateVersion19,
 }
diff --git a/persist/sqlite/sectors.go b/persist/sqlite/sectors.go
index c2c069ca..e6092e4d 100644
--- a/persist/sqlite/sectors.go
+++ b/persist/sqlite/sectors.go
@@ -99,7 +99,7 @@ func (s *Store) SectorLocation(root types.Hash256) (storage.SectorLocation, func
 		} else if err != nil {
 			return fmt.Errorf("failed to get sector id: %w", err)
 		}
-		location, err = sectorLocation(tx, sectorID)
+		location, err = sectorLocation(tx, sectorID, root)
 		if err != nil {
 			return fmt.Errorf("failed to get sector location: %w", err)
 		}
diff --git a/persist/sqlite/volumes.go b/persist/sqlite/volumes.go
index fecfc533..68e93201 100644
--- a/persist/sqlite/volumes.go
+++ b/persist/sqlite/volumes.go
@@ -206,7 +206,7 @@ func (s *Store) StoreSector(root types.Hash256, fn func(loc storage.SectorLocati
 	var exists bool
 
 	err := s.transaction(func(tx txn) error {
-		sectorID, err := sectorDBID(tx, root)
+		sectorID, err := insertSectorDBID(tx, root)
 		if err != nil {
 			return fmt.Errorf("failed to get sector id: %w", err)
 		}
@@ -217,8 +217,8 @@ func (s *Store) StoreSector(root types.Hash256, fn func(loc storage.SectorLocati
 			return fmt.Errorf("failed to lock sector: %w", err)
 		}
 
-		// check if the sector already exists
-		location, err = sectorLocation(tx, sectorID)
+		// check if the sector is already stored on disk
+		location, err = sectorLocation(tx, sectorID, root)
 		exists = err == nil
 		if errors.Is(err, storage.ErrSectorNotFound) {
 			location, err = emptyLocation(tx)
@@ -418,34 +418,51 @@ func (s *Store) SetAvailable(volumeID int64, available bool) error {
 	return err
 }
 
-// sectorDBID returns the database ID of a sector.
+// sectorDBID returns the ID of a sector root in the stored_sectors table.
 func sectorDBID(tx txn, root types.Hash256) (id int64, err error) {
-	err = tx.QueryRow(`INSERT INTO stored_sectors (sector_root, last_access_timestamp) VALUES ($1, $2) ON CONFLICT (sector_root) DO UPDATE SET last_access_timestamp=EXCLUDED.last_access_timestamp RETURNING id`, sqlHash256(root), sqlTime(time.Now())).Scan(&id)
+	err = tx.QueryRow(`SELECT id FROM stored_sectors WHERE sector_root=$1`, sqlHash256(root)).Scan(&id)
 	if errors.Is(err, sql.ErrNoRows) {
 		err = storage.ErrSectorNotFound
 	}
 	return
 }
 
+// insertSectorDBID inserts a sector root into the stored_sectors table if it
+// does not already exist. If the sector root already exists, the ID is
+// returned.
+func insertSectorDBID(tx txn, root types.Hash256) (id int64, err error) {
+	id, err = sectorDBID(tx, root)
+	if errors.Is(err, storage.ErrSectorNotFound) {
+		// insert the sector root
+		err = tx.QueryRow(`INSERT INTO stored_sectors (sector_root, last_access_timestamp) VALUES ($1, $2) RETURNING id`, sqlHash256(root), sqlTime(time.Now())).Scan(&id)
+		return
+	}
+	return
+}
+
 // sectorLocation returns the location of a sector.
-func sectorLocation(tx txn, sectorID int64) (loc storage.SectorLocation, err error) {
-	const query = `SELECT v.id, v.volume_id, v.volume_index, s.sector_root
-FROM volume_sectors v 
-INNER JOIN stored_sectors s ON (s.id=v.sector_id)
+func sectorLocation(tx txn, sectorID int64, root types.Hash256) (loc storage.SectorLocation, err error) {
+	const query = `SELECT v.id, v.volume_id, v.volume_index
+FROM volume_sectors v
 WHERE v.sector_id=$1`
-	err = tx.QueryRow(query, sectorID).Scan(&loc.ID, &loc.Volume, &loc.Index, (*sqlHash256)(&loc.Root))
+	err = tx.QueryRow(query, sectorID).Scan(&loc.ID, &loc.Volume, &loc.Index)
 	if errors.Is(err, sql.ErrNoRows) {
 		return storage.SectorLocation{}, storage.ErrSectorNotFound
 	}
+	// note: this is roundabout, but it saves an extra join since all calls to
+	// sectorLocation are preceded by a call to sectorDBID
+	loc.Root = root
 	return
 }
 
 // emptyLocationInVolume returns an empty location in the given volume. If
 // there is no space available, ErrNotEnoughStorage is returned.
 func emptyLocationInVolume(tx txn, volumeID int64) (loc storage.SectorLocation, err error) {
-	const query = `SELECT vs.id, vs.volume_id, vs.volume_index FROM volume_sectors vs
+	const query = `SELECT vs.id, vs.volume_id, vs.volume_index 
+FROM volume_sectors vs INDEXED BY volume_sectors_volume_id_sector_id_volume_index_compound
 LEFT JOIN locked_volume_sectors lvs ON (lvs.volume_sector_id=vs.id)
-WHERE vs.sector_id IS NULL AND lvs.volume_sector_id IS NULL AND vs.volume_id=$1 LIMIT 1;`
+WHERE vs.sector_id IS NULL AND lvs.volume_sector_id IS NULL AND vs.volume_id=$1
+LIMIT 1;`
 	err = tx.QueryRow(query, volumeID).Scan(&loc.ID, &loc.Volume, &loc.Index)
 	if errors.Is(err, sql.ErrNoRows) {
 		err = storage.ErrNotEnoughStorage
@@ -456,8 +473,12 @@ WHERE vs.sector_id IS NULL AND lvs.volume_sector_id IS NULL AND vs.volume_id=$1
 // emptyLocation returns an empty location in a writable volume. If there is no
 // space available, ErrNotEnoughStorage is returned.
 func emptyLocation(tx txn) (storage.SectorLocation, error) {
+	const query = `SELECT id 
+FROM storage_volumes
+WHERE available=true AND read_only=false AND total_sectors-used_sectors > 0
+ORDER BY used_sectors ASC LIMIT 1;`
 	var volumeID int64
-	err := tx.QueryRow(`SELECT id FROM storage_volumes WHERE available=true AND read_only=false AND total_sectors-used_sectors > 0 ORDER BY used_sectors ASC LIMIT 1;`).Scan(&volumeID)
+	err := tx.QueryRow(query).Scan(&volumeID)
 	if errors.Is(err, sql.ErrNoRows) {
 		return storage.SectorLocation{}, storage.ErrNotEnoughStorage
 	} else if err != nil {