tune unbound to take up less memory for our use case

infra/ec2-userdata.sh

@@ -78,10 +78,11 @@ server:
     infra-cache-slabs: 4
     key-cache-slabs: 4
 
-    # Cache sizing (use available RAM)
-    msg-cache-size: 512m
-    rrset-cache-size: 1g
-    key-cache-size: 256m
+    # Cache sizing — values are per-slab (×4 slabs), so total = 4× these values
+    # Only need ~500MB total — TLD/NS records stay hot via LRU, individual A records evict naturally
+    msg-cache-size: 32m
+    rrset-cache-size: 64m
+    key-cache-size: 16m
 
     # Aggressive caching
     cache-min-ttl: 3600