diff --git a/internal/chunker/chunker_test.go b/internal/chunker/chunker_test.go
index f44919f..520bcd6 100644
--- a/internal/chunker/chunker_test.go
+++ b/internal/chunker/chunker_test.go
@@ -53,7 +53,7 @@ func TestChunkerLargeFileMultipleChunks(t *testing.T) {
 	}
 
 	// Verify chunks reconstruct original data
-	var reconstructed []byte
+	reconstructed := make([]byte, 0, len(data))
 	for _, chunk := range chunks {
 		reconstructed = append(reconstructed, chunk.Data...)
 	}
diff --git a/internal/snapshot/scanner.go b/internal/snapshot/scanner.go
index 8e4b5cd..fc00251 100644
--- a/internal/snapshot/scanner.go
+++ b/internal/snapshot/scanner.go
@@ -624,11 +624,11 @@ func (s *Scanner) collectBatchFlushData(
 
 	collectStart := time.Now()
 
-	var (
-		allFileChunks []database.FileChunk
-		allChunkFiles []database.ChunkFile
-	)
-
+	// Every pending file contributes at least one file-chunk and one
+	// chunk-file mapping, so the file count is a safe lower bound for the
+	// initial capacity of both slices.
+	allFileChunks := make([]database.FileChunk, 0, len(canFlush))
+	allChunkFiles := make([]database.ChunkFile, 0, len(canFlush))
 	allFileIDs := make([]types.FileID, 0, len(canFlush))
 	allFiles := make([]*database.File, 0, len(canFlush))