diff --git a/packages/app/src/Cache/IndexedDB.ts b/packages/app/src/Cache/IndexedDB.ts
index df0fe97a..5fa7b959 100644
--- a/packages/app/src/Cache/IndexedDB.ts
+++ b/packages/app/src/Cache/IndexedDB.ts
@@ -1,7 +1,7 @@
 import Dexie, { Table } from "dexie";
 import { TaggedNostrEvent, ReqFilter as Filter } from "@snort/system";
 import * as Comlink from "comlink";
-import LRUSet from "@/Cache/LRUSet";
+import LRUSet from "@snort/shared/src/LRUSet";
 
 type Tag = {
   id: string;
diff --git a/packages/app/src/Cache/LRUSet.ts b/packages/shared/src/LRUSet.ts
similarity index 100%
rename from packages/app/src/Cache/LRUSet.ts
rename to packages/shared/src/LRUSet.ts
diff --git a/packages/system/src/connection.ts b/packages/system/src/connection.ts
index ec51ce99..86660060 100644
--- a/packages/system/src/connection.ts
+++ b/packages/system/src/connection.ts
@@ -9,6 +9,8 @@ import { ConnectionStats } from "./connection-stats";
 import { NostrEvent, ReqCommand, ReqFilter, TaggedNostrEvent, u256 } from "./nostr";
 import { RelayInfo } from "./relay-info";
 import EventKind from "./event-kind";
+import seenEvents from "./seen-events";
+import {getHex64} from "./utils";
 
 /**
  * Relay settings
@@ -199,6 +201,14 @@ export class Connection extends EventEmitter<ConnectionEvents> {
   OnMessage(e: WebSocket.MessageEvent) {
     this.#activity = unixNowMs();
     if ((e.data as string).length > 0) {
+      // skip message processing if we've already seen it
+      const msgId = getHex64(e.data as string, "id");
+      if (seenEvents.has(msgId)) {
+        console.log('already seen');
+        return;
+      }
+      seenEvents.add(msgId); // TODO only do after msg validation
+
       const msg = JSON.parse(e.data as string) as Array<string | NostrEvent | boolean>;
       const tag = msg[0] as string;
       switch (tag) {
diff --git a/packages/system/src/seen-events.ts b/packages/system/src/seen-events.ts
new file mode 100644
index 00000000..20a9cf85
--- /dev/null
+++ b/packages/system/src/seen-events.ts
@@ -0,0 +1,3 @@
+import LRUSet from "@snort/shared/src/LRUSet";
+
+export default new LRUSet<string>(2000);
\ No newline at end of file
diff --git a/packages/system/src/utils.ts b/packages/system/src/utils.ts
index 6bfd3802..2787d54b 100644
--- a/packages/system/src/utils.ts
+++ b/packages/system/src/utils.ts
@@ -82,3 +82,10 @@ export function parseIMeta(tags: Array<Array<string>>) {
   }
   return ret;
 }
+
+export function getHex64(json: string, field: string): string {
+  let len = field.length + 3
+  let idx = json.indexOf(`"${field}":`) + len
+  let s = json.slice(idx).indexOf(`"`) + idx + 1
+  return json.slice(s, s + 64)
+}