diff --git a/upb_table.h b/upb_table.h
index 41cc2f7e78..5a23ae56a3 100644
--- a/upb_table.h
+++ b/upb_table.h
@@ -64,6 +64,11 @@ inline struct upb_inttable_entry *upb_inttable_mainpos(
 inline void *upb_inttable_lookup(struct upb_inttable *table,
                                  int32_t key,
                                  int32_t entry_size) {
+  /* TODO: experiment with Cuckoo Hashing, which can perform lookups without
+   * any branches, cf:
+   * http://www.cs.cmu.edu/~damon2006/pdf/zukowski06archconscioushashing.pdf.
+   * The tradeoff is having to calculate a second hash for every lookup, which
+   * will hurt the simple array case. */
   struct upb_inttable_entry *e = upb_inttable_mainpos2(table, key, entry_size);
   do {
     if (key == e->key) return e;