diff --git a/tsdb/tsm1/reader_prefix_tree.go b/tsdb/tsm1/reader_prefix_tree.go
index b03f08a53e..059de6c04d 100644
--- a/tsdb/tsm1/reader_prefix_tree.go
+++ b/tsdb/tsm1/reader_prefix_tree.go
@@ -6,6 +6,12 @@ type prefixTreeKey [8]byte
 
 const prefixTreeKeySize = len(prefixTreeKey{})
 
+// prefixTree is a type that keeps track of a slice of time ranges for prefixes and allows
+// querying for all of the time ranges for prefixes that match a provided key. It chunks
+// added prefixes by 8 bytes and then by 1 byte because typical prefixes will be 8 or 16
+// bytes. This allows for effectively O(1) searches, but degrades to O(len(key)) in the
+// worst case when there is a matching prefix for every byte of the key. Appending a prefix
+// is similar.
 type prefixTree struct {
 	values []TimeRange
 	short  map[byte]*prefixTree
diff --git a/tsdb/tsm1/reader_prefix_tree_test.go b/tsdb/tsm1/reader_prefix_tree_test.go
index 955901dadd..392523639b 100644
--- a/tsdb/tsm1/reader_prefix_tree_test.go
+++ b/tsdb/tsm1/reader_prefix_tree_test.go
@@ -45,6 +45,36 @@ func TestPrefixTree(t *testing.T) {
 	})
 }
 
+// Typical results on a 2018 MPB. Pay special attention to the
+// 8 and 16 results as they are the most likely.
+//
+// BenchmarkPrefixTree/Append/0-8           300000000       5.93 ns/op
+// BenchmarkPrefixTree/Append/4-8            20000000      93.7  ns/op
+// BenchmarkPrefixTree/Append/8-8           100000000      12.9  ns/op
+// BenchmarkPrefixTree/Append/12-8           20000000     100.0  ns/op
+// BenchmarkPrefixTree/Append/16-8          100000000      20.4  ns/op
+// BenchmarkPrefixTree/Append/20-8           20000000     111.0  ns/op
+// BenchmarkPrefixTree/Append/24-8           50000000      28.5  ns/op
+// BenchmarkPrefixTree/Append/28-8           20000000     118.0  ns/op
+// BenchmarkPrefixTree/Append/32-8           50000000      35.8  ns/op
+// BenchmarkPrefixTree/Search/Best/0-8      300000000       5.76 ns/op
+// BenchmarkPrefixTree/Search/Best/4-8       20000000     102.0  ns/op
+// BenchmarkPrefixTree/Search/Best/8-8      100000000      18.5  ns/op
+// BenchmarkPrefixTree/Search/Best/12-8      20000000     116.0  ns/op
+// BenchmarkPrefixTree/Search/Best/16-8      50000000      31.9  ns/op
+// BenchmarkPrefixTree/Search/Best/20-8      10000000     131.0  ns/op
+// BenchmarkPrefixTree/Search/Best/24-8      30000000      45.3  ns/op
+// BenchmarkPrefixTree/Search/Best/28-8      10000000     142.0  ns/op
+// BenchmarkPrefixTree/Search/Best/32-8      20000000      58.0  ns/op
+// BenchmarkPrefixTree/Search/Worst/0-8     300000000       5.79 ns/op
+// BenchmarkPrefixTree/Search/Worst/4-8      20000000      79.2  ns/op
+// BenchmarkPrefixTree/Search/Worst/8-8      10000000     199.0  ns/op
+// BenchmarkPrefixTree/Search/Worst/12-8      5000000     301.0  ns/op
+// BenchmarkPrefixTree/Search/Worst/16-8      3000000     422.0  ns/op
+// BenchmarkPrefixTree/Search/Worst/20-8      3000000     560.0  ns/op
+// BenchmarkPrefixTree/Search/Worst/24-8      2000000     683.0  ns/op
+// BenchmarkPrefixTree/Search/Worst/28-8      2000000     772.0  ns/op
+// BenchmarkPrefixTree/Search/Worst/32-8      2000000     875.0  ns/op
 func BenchmarkPrefixTree(b *testing.B) {
 	b.Run("Append", func(b *testing.B) {
 		run := func(b *testing.B, prefix []byte) {
diff --git a/tsdb/tsm1/reader_time_range.go b/tsdb/tsm1/reader_time_range.go
index a588799de7..a800df5005 100644
--- a/tsdb/tsm1/reader_time_range.go
+++ b/tsdb/tsm1/reader_time_range.go
@@ -51,7 +51,7 @@ func timeRangesCoverEntries(merger timeRangeMerger, entries []IndexEntry) (cover
 	return len(entries) == 0
 }
 
-// timeRangeMerger is a special purpose data structure to merge three sources off
+// timeRangeMerger is a special purpose data structure to merge three sources of
 // TimeRanges so that we can check if they cover a slice of index entries.
 type timeRangeMerger struct {
 	sorted   []TimeRange