diff --git a/ansible/roles/bitcoin_knots/defaults/main.yml b/ansible/roles/bitcoin_knots/defaults/main.yml
index 01a352d..cce3850 100644
--- a/ansible/roles/bitcoin_knots/defaults/main.yml
+++ b/ansible/roles/bitcoin_knots/defaults/main.yml
@@ -69,11 +69,17 @@ healthcheck_push_token: ""
 bitcoin_logfile: "{{ bitcoin_data_dir }}/debug.log"
 
 # --- dbcache ----------------------------------------------------------------
-# Computed as 90% of RAM unless this is set. The live node was hand-tuned to
-# 200 MB; the calculation would have produced 3528. As with fulcrum, note that
+# Computed as 90% of RAM unless this is set. As with fulcrum, note that
 # set_fact outranks role defaults, so the CALCULATION has to honour this - a
 # value pinned only in defaults/ is silently ignored.
-bitcoin_dbcache_mb_override: 200
+#
+# 1200, raised from a hand-tuned 200 on 2026-10-18. At 200 MB almost no UTXO
+# lookup hit memory: the P2P thread alone read ~4 MB/s off the saturated HDD
+# mirror validating relayed transactions, and block validation took a median
+# 11 s, p90 103 s, max 344 s - long enough for RPC to stall and the health
+# probe to fail. 1200 is what fits in the 4 GB VM (bitcoind ~1.5 GB RSS at
+# 200, mempool ~3 MB in practice). Raising the VM to 6 GB would allow ~3000.
+bitcoin_dbcache_mb_override: 1200
 
 # --- DATUM Gateway ----------------------------------------------------------
 # This node feeds block templates to datum_gateway on knots-box. These settings