diff --git a/go/util/util.go b/go/util/util.go
index 57c855c..8d750e5 100644
--- a/go/util/util.go
+++ b/go/util/util.go
@@ -499,6 +499,15 @@
 	return rv
 }
 
+// CopyString returns a copy of the given string. This may seem unnecessary, but
+// is very important at preventing leaks of strings. For example, subslicing
+// a string can prevent the larger string from being cleaned up.
+func CopyString(s string) string {
+	b := &strings.Builder{}
+	b.WriteString(s)
+	return b.String()
+}
+
 // KeysOfParamSet returns the keys of a param set.
 func KeysOfParamSet(set map[string][]string) []string {
 	ret := make([]string, 0, len(set))
diff --git a/golden/go/indexer/indexer.go b/golden/go/indexer/indexer.go
index ffb283f..918f812 100644
--- a/golden/go/indexer/indexer.go
+++ b/golden/go/indexer/indexer.go
@@ -507,8 +507,8 @@
 		t := idx.cpxTile.GetTile(is)
 		for id, tr := range t.Traces {
 			gt, ok := tr.(*types.GoldenTrace)
-			if !ok {
-				sklog.Warningf("Unexpected trace type: %#v", gt)
+			if !ok || gt == nil {
+				sklog.Warningf("Unexpected trace type for id %s: %#v", id, gt)
 				continue
 			}
 			tp := types.TracePair{
@@ -619,7 +619,7 @@
 		byTest := idx.DigestCountsByTest(types.IncludeIgnoredTraces)
 		unavailableDigests, err := idx.diffStore.UnavailableDigests(ctx)
 		if err != nil {
-			sklog.Warningf("could not fetch unavailables digests, going to assume all are valid: %s", err)
+			sklog.Warningf("could not fetch unavailable digests, going to assume all are valid: %s", err)
 			unavailableDigests = nil
 		}
 		// Collect all hashes in the tile that haven't been marked as unavailable yet.
@@ -661,18 +661,19 @@
 	}
 	d := digesttools.NewClosestDiffFinder(exp, idx.dCounters[is], idx.diffStore)
 
-	go func() {
+	// Pass these in so as to allow the rest of the items in the index to be GC'd if needed.
+	go func(warmer warmer.DiffWarmer, summaries countsAndBlames, tests types.TestNameSet, dc digest_counter.DigestCounter, d digesttools.ClosestDiffFinder) {
 		// If there are somehow lots and lots of diffs or the warmer gets stuck, we should bail out
 		// at some point to prevent amount of work being done on the diffstore (e.g. a remote
 		// diffserver) from growing in an unbounded fashion.
 		// 15 minutes was chosen based on the 90th percentile time looking at the metrics.
 		ctx, cancel := context.WithTimeout(context.Background(), 15*time.Minute)
 		defer cancel()
-		err := idx.warmer.PrecomputeDiffs(ctx, idx.summaries[is], idx.testNames, idx.dCounters[is], d)
-		if err != nil {
-			sklog.Warningf("Could not precompute diffs for %d summaries and %d test names: %s", len(idx.summaries[is]), len(idx.testNames), err)
+
+		if err := warmer.PrecomputeDiffs(ctx, summaries, tests, dc, d); err != nil {
+			sklog.Warningf("Could not precompute diffs for %d summaries and %d test names: %s", len(summaries), len(tests), err)
 		}
-	}()
+	}(idx.warmer, idx.summaries[is], idx.testNames, idx.dCounters[is], d)
 	return nil
 }
 
diff --git a/golden/go/tracestore/bt_tracestore/types.go b/golden/go/tracestore/bt_tracestore/types.go
index a75e010..ee8c5d9 100644
--- a/golden/go/tracestore/bt_tracestore/types.go
+++ b/golden/go/tracestore/bt_tracestore/types.go
@@ -306,7 +306,7 @@
 	if ok {
 		return d
 	}
-	d = fromBytes(b)
+	d = fromBytes(k[:])
 	c[k] = d
 	return d
 }
diff --git a/golden/go/tracestore/bt_tracestore/util.go b/golden/go/tracestore/bt_tracestore/util.go
index bb64712..dc17624 100644
--- a/golden/go/tracestore/bt_tracestore/util.go
+++ b/golden/go/tracestore/bt_tracestore/util.go
@@ -10,6 +10,7 @@
 	"go.skia.org/infra/go/paramtools"
 	"go.skia.org/infra/go/query"
 	"go.skia.org/infra/go/sklog"
+	"go.skia.org/infra/go/util"
 	"go.skia.org/infra/golden/go/tracestore"
 	"go.skia.org/infra/golden/go/types"
 )
@@ -49,7 +50,10 @@
 	if len(parts) == 0 {
 		return ""
 	}
-	return parts[len(parts)-1]
+	// We shouldn't return the result directly out of split, lest it
+	// leak the BigTable row (and potentially all the data associated with it).
+	// https://go101.org/article/memory-leaking.html
+	return util.CopyString(parts[len(parts)-1])
 }
 
 // toBytes turns a Digest into the bytes that will be stored in the table.
diff --git a/perf/go/btts/btts.go b/perf/go/btts/btts.go
index 913a196..77660ef 100644
--- a/perf/go/btts/btts.go
+++ b/perf/go/btts/btts.go
@@ -29,6 +29,7 @@
 	"go.skia.org/infra/go/skerr"
 	"go.skia.org/infra/go/sklog"
 	"go.skia.org/infra/go/timer"
+	"go.skia.org/infra/go/util"
 	"go.skia.org/infra/go/vec32"
 	"go.skia.org/infra/perf/go/btts/engine"
 	"go.skia.org/infra/perf/go/config"
@@ -1034,9 +1035,9 @@
 			g.Go(func() error {
 				return b.getTable().ReadRows(tctx, bigtable.PrefixRange(tileKey.TraceRowPrefix(i)), func(row bigtable.Row) bool {
 					parts := strings.Split(row.Key(), ":")
-					b := &strings.Builder{}
-					b.WriteString(parts[2])
-					out <- b.String()
+					// prevent leaking the row data from the slice.
+					// https://go101.org/article/memory-leaking.html
+					out <- util.CopyString(parts[2])
 					return true
 				}, bigtable.RowFilter(
 					bigtable.ChainFilters(