diff --git a/deno.json b/deno.json
index 0867a999..aa9729e1 100644
--- a/deno.json
+++ b/deno.json
@@ -26,6 +26,7 @@
     "@db/sqlite": "jsr:@db/sqlite@^0.11.1",
     "@hono/hono": "jsr:@hono/hono@^4.4.6",
     "@isaacs/ttlcache": "npm:@isaacs/ttlcache@^1.4.1",
+    "@lambdalisue/async": "jsr:@lambdalisue/async@^2.1.1",
     "@noble/secp256k1": "npm:@noble/secp256k1@^2.0.0",
     "@nostrify/nostrify": "jsr:@nostrify/nostrify@^0.28.0",
     "@scure/base": "npm:@scure/base@^1.1.6",
@@ -42,8 +43,8 @@
     "@std/media-types": "jsr:@std/media-types@^0.224.1",
     "@std/streams": "jsr:@std/streams@^0.223.0",
     "comlink": "npm:comlink@^4.4.1",
-    "deno.json": "./deno.json",
     "deno-safe-fetch/load": "https://gitlab.com/soapbox-pub/deno-safe-fetch/-/raw/v1.0.0/load.ts",
+    "deno.json": "./deno.json",
     "entities": "npm:entities@^4.5.0",
     "fast-stable-stringify": "npm:fast-stable-stringify@^1.0.0",
     "formdata-helper": "npm:formdata-helper@^0.3.0",
@@ -51,7 +52,6 @@
     "iso-639-1": "npm:iso-639-1@2.1.15",
     "isomorphic-dompurify": "npm:isomorphic-dompurify@^2.11.0",
     "kysely": "npm:kysely@^0.27.4",
-    "postgres": "https://raw.githubusercontent.com/xyzshantaram/postgres.js/8a9bbce88b3f6425ecaacd99a80372338b157a53/deno/mod.js",
     "kysely-postgres-js": "npm:kysely-postgres-js@2.0.0",
     "light-bolt11-decoder": "npm:light-bolt11-decoder",
     "linkify-plugin-hashtag": "npm:linkify-plugin-hashtag@^4.1.1",
@@ -61,6 +61,7 @@
     "nostr-relaypool": "npm:nostr-relaypool2@0.6.34",
     "nostr-tools": "npm:nostr-tools@2.5.1",
     "nostr-wasm": "npm:nostr-wasm@^0.1.0",
+    "postgres": "https://raw.githubusercontent.com/xyzshantaram/postgres.js/8a9bbce88b3f6425ecaacd99a80372338b157a53/deno/mod.js",
     "prom-client": "npm:prom-client@^15.1.2",
     "question-deno": "https://raw.githubusercontent.com/ocpu/question-deno/10022b8e52555335aa510adb08b0a300df3cf904/mod.ts",
     "tldts": "npm:tldts@^6.0.14",
diff --git a/deno.lock b/deno.lock
index b33fa3ed..2f1f6090 100644
--- a/deno.lock
+++ b/deno.lock
@@ -10,6 +10,7 @@
       "jsr:@gleasonator/policy@0.4.0": "jsr:@gleasonator/policy@0.4.0",
       "jsr:@gleasonator/policy@0.4.1": "jsr:@gleasonator/policy@0.4.1",
       "jsr:@hono/hono@^4.4.6": "jsr:@hono/hono@4.5.3",
+      "jsr:@lambdalisue/async@^2.1.1": "jsr:@lambdalisue/async@2.1.1",
       "jsr:@nostrify/nostrify@^0.22.1": "jsr:@nostrify/nostrify@0.22.5",
       "jsr:@nostrify/nostrify@^0.22.4": "jsr:@nostrify/nostrify@0.22.4",
       "jsr:@nostrify/nostrify@^0.22.5": "jsr:@nostrify/nostrify@0.22.5",
@@ -126,6 +127,9 @@
       "@hono/hono@4.5.3": {
         "integrity": "429923b2b3c6586a1450862328d61a1346fee5841e8ae86c494250475057213c"
       },
+      "@lambdalisue/async@2.1.1": {
+        "integrity": "1fc9bc6f4ed50215cd2f7217842b18cea80f81c25744f88f8c5eb4be5a1c9ab4"
+      },
       "@nostrify/nostrify@0.22.4": {
         "integrity": "1c8a7847e5773213044b491e85fd7cafae2ad194ce59da4d957d2b27c776b42d",
         "dependencies": [
@@ -1780,6 +1784,7 @@
       "jsr:@bradenmacdonald/s3-lite-client@^0.7.4",
       "jsr:@db/sqlite@^0.11.1",
       "jsr:@hono/hono@^4.4.6",
+      "jsr:@lambdalisue/async@^2.1.1",
       "jsr:@nostrify/nostrify@^0.28.0",
       "jsr:@soapbox/kysely-deno-sqlite@^2.1.0",
       "jsr:@soapbox/stickynotes@^0.4.0",
diff --git a/src/config.ts b/src/config.ts
index dfb84618..56825cc0 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -242,6 +242,10 @@ class Conf {
   static get firehoseEnabled(): boolean {
     return optionalBooleanSchema.parse(Deno.env.get('FIREHOSE_ENABLED')) ?? true;
   }
+  /** Number of events the firehose is allowed to process at one time before they have to wait in a queue. */
+  static get firehoseConcurrency(): number {
+    return Math.ceil(Number(Deno.env.get('FIREHOSE_CONCURRENCY') ?? (Conf.pg.poolSize * 0.25)));
+  }
   /** Whether to enable Ditto cron jobs. */
   static get cronEnabled(): boolean {
     return optionalBooleanSchema.parse(Deno.env.get('CRON_ENABLED')) ?? true;
diff --git a/src/firehose.ts b/src/firehose.ts
index 8b61c784..86d19f74 100644
--- a/src/firehose.ts
+++ b/src/firehose.ts
@@ -1,5 +1,7 @@
+import { Semaphore } from '@lambdalisue/async';
 import { Stickynotes } from '@soapbox/stickynotes';
 
+import { Conf } from '@/config.ts';
 import { firehoseEventCounter } from '@/metrics.ts';
 import { Storages } from '@/storages.ts';
 import { nostrNow } from '@/utils.ts';
@@ -7,6 +9,7 @@ import { nostrNow } from '@/utils.ts';
 import * as pipeline from '@/pipeline.ts';
 
 const console = new Stickynotes('ditto:firehose');
+const sem = new Semaphore(Conf.firehoseConcurrency);
 
 /**
  * This function watches events on all known relays and performs
@@ -22,9 +25,13 @@ export async function startFirehose(): Promise<void> {
       console.debug(`NostrEvent<${event.kind}> ${event.id}`);
       firehoseEventCounter.inc({ kind: event.kind });
 
-      pipeline
-        .handleEvent(event, AbortSignal.timeout(5000))
-        .catch(() => {});
+      sem.lock(async () => {
+        try {
+          await pipeline.handleEvent(event, AbortSignal.timeout(5000));
+        } catch (e) {
+          console.warn(e);
+        }
+      });
     }
   }
 }