diff --git a/index.ts b/index.ts
index eda6ea3..29f075f 100644
--- a/index.ts
+++ b/index.ts
@@ -3,14 +3,15 @@ export * from './relay'
 export * from './event'
 export * from './filter'
 
-export * as fj from './fakejson'
-
 export * as nip04 from './nip04'
 export * as nip05 from './nip05'
 export * as nip06 from './nip06'
 export * as nip19 from './nip19'
 export * as nip26 from './nip26'
 
+export * as fj from './fakejson'
+export * as utils from './utils'
+
 // monkey patch secp256k1
 import * as secp256k1 from '@noble/secp256k1'
 import {hmac} from '@noble/hashes/hmac'
diff --git a/package.json b/package.json
index 76bf071..1669c9a 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "nostr-tools",
-  "version": "1.2.0",
+  "version": "1.2.1",
   "description": "Tools for making a Nostr client.",
   "repository": {
     "type": "git",
diff --git a/utils.test.js b/utils.test.js
new file mode 100644
index 0000000..a86aba7
--- /dev/null
+++ b/utils.test.js
@@ -0,0 +1,183 @@
+/* eslint-env jest */
+
+const {utils} = require('./lib/nostr.cjs')
+
+const {insertEventIntoAscendingList, insertEventIntoDescendingList} = utils
+
+describe('inserting into a desc sorted list of events', () => {
+  test('insert into an empty list', async () => {
+    const list0 = []
+    expect(
+      insertEventIntoDescendingList(list0, {id: 'abc', created_at: 10})
+    ).toHaveLength(1)
+  })
+
+  test('insert in the beginning of a list', async () => {
+    const list0 = [{created_at: 20}, {created_at: 10}]
+    const list1 = insertEventIntoDescendingList(list0, {
+      id: 'abc',
+      created_at: 30
+    })
+    expect(list1).toHaveLength(3)
+    expect(list1[0].id).toBe('abc')
+  })
+
+  test('insert in the beginning of a list with same created_at', async () => {
+    const list0 = [{created_at: 30}, {created_at: 20}, {created_at: 10}]
+    const list1 = insertEventIntoDescendingList(list0, {
+      id: 'abc',
+      created_at: 30
+    })
+    expect(list1).toHaveLength(4)
+    expect(list1[0].id).toBe('abc')
+  })
+
+  test('insert in the middle of a list', async () => {
+    const list0 = [
+      {created_at: 30},
+      {created_at: 20},
+      {created_at: 10},
+      {created_at: 1}
+    ]
+    const list1 = insertEventIntoDescendingList(list0, {
+      id: 'abc',
+      created_at: 15
+    })
+    expect(list1).toHaveLength(5)
+    expect(list1[2].id).toBe('abc')
+  })
+
+  test('insert in the end of a list', async () => {
+    const list0 = [
+      {created_at: 20},
+      {created_at: 20},
+      {created_at: 20},
+      {created_at: 20},
+      {created_at: 10}
+    ]
+    const list1 = insertEventIntoDescendingList(list0, {
+      id: 'abc',
+      created_at: 5
+    })
+    expect(list1).toHaveLength(6)
+    expect(list1.slice(-1)[0].id).toBe('abc')
+  })
+
+  test('insert in the last-to-end of a list with same created_at', async () => {
+    const list0 = [
+      {created_at: 20},
+      {created_at: 20},
+      {created_at: 20},
+      {created_at: 20},
+      {created_at: 10}
+    ]
+    const list1 = insertEventIntoDescendingList(list0, {
+      id: 'abc',
+      created_at: 10
+    })
+    expect(list1).toHaveLength(6)
+    expect(list1.slice(-2)[0].id).toBe('abc')
+  })
+
+  test('do not insert duplicates', async () => {
+    const list0 = [
+      {created_at: 20},
+      {created_at: 20},
+      {created_at: 10, id: 'abc'}
+    ]
+    const list1 = insertEventIntoDescendingList(list0, {
+      id: 'abc',
+      created_at: 10
+    })
+    expect(list1).toHaveLength(3)
+  })
+})
+
+describe('inserting into a asc sorted list of events', () => {
+  test('insert into an empty list', async () => {
+    const list0 = []
+    expect(
+      insertEventIntoAscendingList(list0, {id: 'abc', created_at: 10})
+    ).toHaveLength(1)
+  })
+
+  test('insert in the beginning of a list', async () => {
+    const list0 = [{created_at: 10}, {created_at: 20}]
+    const list1 = insertEventIntoAscendingList(list0, {
+      id: 'abc',
+      created_at: 1
+    })
+    expect(list1).toHaveLength(3)
+    expect(list1[0].id).toBe('abc')
+  })
+
+  test('insert in the beginning of a list with same created_at', async () => {
+    const list0 = [{created_at: 10}, {created_at: 20}, {created_at: 30}]
+    const list1 = insertEventIntoAscendingList(list0, {
+      id: 'abc',
+      created_at: 10
+    })
+    expect(list1).toHaveLength(4)
+    expect(list1[0].id).toBe('abc')
+  })
+
+  test('insert in the middle of a list', async () => {
+    const list0 = [
+      {created_at: 10},
+      {created_at: 20},
+      {created_at: 30},
+      {created_at: 40}
+    ]
+    const list1 = insertEventIntoAscendingList(list0, {
+      id: 'abc',
+      created_at: 25
+    })
+    expect(list1).toHaveLength(5)
+    expect(list1[2].id).toBe('abc')
+  })
+
+  test('insert in the end of a list', async () => {
+    const list0 = [
+      {created_at: 20},
+      {created_at: 20},
+      {created_at: 20},
+      {created_at: 20},
+      {created_at: 40}
+    ]
+    const list1 = insertEventIntoAscendingList(list0, {
+      id: 'abc',
+      created_at: 50
+    })
+    expect(list1).toHaveLength(6)
+    expect(list1.slice(-1)[0].id).toBe('abc')
+  })
+
+  test('insert in the last-to-end of a list with same created_at', async () => {
+    const list0 = [
+      {created_at: 20},
+      {created_at: 20},
+      {created_at: 20},
+      {created_at: 20},
+      {created_at: 30}
+    ]
+    const list1 = insertEventIntoAscendingList(list0, {
+      id: 'abc',
+      created_at: 30
+    })
+    expect(list1).toHaveLength(6)
+    expect(list1.slice(-2)[0].id).toBe('abc')
+  })
+
+  test('do not insert duplicates', async () => {
+    const list0 = [
+      {created_at: 20},
+      {created_at: 20},
+      {created_at: 30, id: 'abc'}
+    ]
+    const list1 = insertEventIntoAscendingList(list0, {
+      id: 'abc',
+      created_at: 30
+    })
+    expect(list1).toHaveLength(3)
+  })
+})
diff --git a/utils.ts b/utils.ts
index 784a868..787afd5 100644
--- a/utils.ts
+++ b/utils.ts
@@ -1,2 +1,97 @@
+import {Event} from './event'
+
 export const utf8Decoder = new TextDecoder('utf-8')
 export const utf8Encoder = new TextEncoder()
+
+//
+// fast insert-into-sorted-array functions adapted from https://github.com/terrymorse58/fast-sorted-array
+//
+export function insertEventIntoDescendingList(
+  sortedArray: Event[],
+  event: Event
+) {
+  let start = 0
+  let end = sortedArray.length - 1
+  let midPoint
+  let position = start
+
+  if (end < 0) {
+    position = 0
+  } else if (event.created_at < sortedArray[end].created_at) {
+    position = end + 1
+  } else if (event.created_at >= sortedArray[start].created_at) {
+    position = start
+  } else
+    while (true) {
+      if (end <= start + 1) {
+        position = end
+        break
+      }
+      midPoint = Math.floor(start + (end - start) / 2)
+      if (sortedArray[midPoint].created_at > event.created_at) {
+        start = midPoint
+      } else if (sortedArray[midPoint].created_at < event.created_at) {
+        end = midPoint
+      } else {
+        // aMidPoint === num
+        position = midPoint
+        break
+      }
+    }
+
+  // insert when num is NOT already in (no duplicates)
+  if (sortedArray[position]?.id !== event.id) {
+    return [
+      ...sortedArray.slice(0, position),
+      event,
+      ...sortedArray.slice(position)
+    ]
+  }
+
+  return sortedArray
+}
+
+export function insertEventIntoAscendingList(
+  sortedArray: Event[],
+  event: Event
+) {
+  let start = 0
+  let end = sortedArray.length - 1
+  let midPoint
+  let position = start
+
+  if (end < 0) {
+    position = 0
+  } else if (event.created_at > sortedArray[end].created_at) {
+    position = end + 1
+  } else if (event.created_at <= sortedArray[start].created_at) {
+    position = start
+  } else
+    while (true) {
+      if (end <= start + 1) {
+        position = end
+        break
+      }
+      midPoint = Math.floor(start + (end - start) / 2)
+      if (sortedArray[midPoint].created_at < event.created_at) {
+        start = midPoint
+      } else if (sortedArray[midPoint].created_at > event.created_at) {
+        end = midPoint
+      } else {
+        // aMidPoint === num
+        position = midPoint
+        break
+      }
+    }
+
+  // insert when num is NOT already in (no duplicates)
+  if (sortedArray[position]?.id !== event.id) {
+    return [
+      ...sortedArray.slice(0, position),
+      event,
+      ...sortedArray.slice(position)
+    ]
+  }
+
+  return sortedArray
+}