diff --git a/.eslintrc.json b/.eslintrc.json
index 3de38b4..45ef023 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -1,19 +1,9 @@
 {
   "env": {
-    "es6": true,
+    "es2022": true,
     "node": true
   },
   "extends": "eslint:recommended",
-  "globals": {
-    "Atomics": "readable",
-    "BigInt": "readable",
-    "BigInt64Array": "readable",
-    "BigUint64Array": "readable",
-    "queueMicrotask": "readable",
-    "SharedArrayBuffer": "readable",
-    "TextEncoder": "readable",
-    "TextDecoder": "readable"
-  },
   "overrides": [
     {
       "files": ["*.mjs"],
@@ -44,9 +34,8 @@
       }
     }
   ],
-  "parser": "babel-eslint",
   "parserOptions": {
-    "ecmaVersion": 10,
+    "ecmaVersion": 13,
     "ecmaFeatures": {
       "globalReturn": true
     },
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 67fede4..11d1fc0 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -24,6 +24,10 @@ jobs:
     - name: Lint
       run: npm run lint
 
+    - name: Lint types
+      run: npm run lint-types
+
+
   test:
     name: Test
     runs-on: ${{ matrix.os }}
diff --git a/lib/lru.js b/lib/lru.js
index 454e2b1..c0998fe 100644
--- a/lib/lru.js
+++ b/lib/lru.js
@@ -10,18 +10,20 @@ const assert = require('bsert');
 
 /**
  * LRU Cache
+ * @template K - Key type
+ * @template V - Value type
  */
 
 class LRU {
-  /** @type {Map} */
+  /** @type {Map<K, LRUItem<K, V>>} */
   map;
 
   /**
    * Create an LRU cache.
    * @constructor
    * @param {Number} capacity
-   * @param {Function?} getSize
-   * @param {Function?} CustomMap
+   * @param {Function} [getSize]
+   * @param {Function} [CustomMap]
    */
 
   constructor(capacity, getSize, CustomMap) {
@@ -34,8 +36,11 @@ class LRU {
     this.map = CustomMap ? new CustomMap() : new Map();
     this.size = 0;
     this.items = 0;
+    /** @type {LRUItem<K, V>?} */
     this.head = null;
+    /** @type {LRUItem<K, V>?} */
     this.tail = null;
+    /** @type {LRUBatch<K, V>?} */
     this.pending = null;
 
     this.capacity = capacity;
@@ -45,7 +50,7 @@ class LRU {
   /**
    * Calculate size of an item.
    * @private
-   * @param {LRUItem} item
+   * @param {LRUItem<K, V>} item
    * @returns {Number} Size.
    */
 
@@ -65,7 +70,9 @@ class LRU {
     if (this.size <= this.capacity)
       return;
 
+    /** @type {LRUItem<K, V>?} */
     let item = null;
+    /** @type {LRUItem<K, V>?} */
     let next = null;
 
     for (item = this.head; item; item = next) {
@@ -116,8 +123,8 @@ class LRU {
 
   /**
    * Add an item to the cache.
-   * @param {String|Number} key
-   * @param {Object} value
+   * @param {K} key
+   * @param {V} value
    */
 
   set(key, value) {
@@ -150,8 +157,8 @@ class LRU {
 
   /**
    * Retrieve an item from the cache.
-   * @param {String|Number} key
-   * @returns {Object} Item.
+   * @param {K} key
+   * @returns {V} Item.
    */
 
   get(key) {
@@ -171,7 +178,7 @@ class LRU {
 
   /**
    * Test whether the cache contains a key.
-   * @param {String|Number} key
+   * @param {K} key
    * @returns {Boolean}
    */
 
@@ -183,7 +190,7 @@ class LRU {
 
   /**
    * Remove an item from the cache.
-   * @param {String|Number} key
+   * @param {K} key
    * @returns {Boolean} Whether an item was removed.
    */
 
@@ -209,7 +216,7 @@ class LRU {
   /**
    * Append an item to the linked list (sets new tail).
    * @private
-   * @param {LRUItem} item
+   * @param {LRUItem<K, V>} item
    */
 
   _appendList(item) {
@@ -219,8 +226,8 @@ class LRU {
   /**
    * Insert item into the linked list.
    * @private
-   * @param {LRUItem|null} ref
-   * @param {LRUItem} item
+   * @param {LRUItem<K, V>?} ref
+   * @param {LRUItem<K, V>} item
    */
 
   _insertList(ref, item) {
@@ -253,7 +260,7 @@ class LRU {
   /**
    * Remove item from the linked list.
    * @private
-   * @param {LRUItem} item
+   * @param {LRUItem<K, V>} item
    */
 
   _removeList(item) {
@@ -281,7 +288,7 @@ class LRU {
 
   /**
    * Collect all keys in the cache, sorted by LRU.
-   * @returns {String[]}
+   * @returns {K[]}
    */
 
   keys() {
@@ -302,7 +309,7 @@ class LRU {
 
   /**
    * Collect all values in the cache, sorted by LRU.
-   * @returns {String[]}
+   * @returns {V[]}
    */
 
   values() {
@@ -316,7 +323,7 @@ class LRU {
 
   /**
    * Convert the LRU cache to an array of items.
-   * @returns {Object[]}
+   * @returns {LRUItem<K, V>[]}
    */
 
   toArray() {
@@ -331,7 +338,7 @@ class LRU {
   /**
    * Create an atomic batch for the lru
    * (used for caching database writes).
-   * @returns {LRUBatch}
+   * @returns {LRUBatch<K, V>}
    */
 
   batch() {
@@ -377,8 +384,8 @@ class LRU {
 
   /**
    * Push an item onto the pending batch.
-   * @param {String} key
-   * @param {Object} value
+   * @param {K} key
+   * @param {V} value
    */
 
   push(key, value) {
@@ -392,7 +399,7 @@ class LRU {
 
   /**
    * Push a removal onto the pending batch.
-   * @param {String} key
+   * @param {K} key
    */
 
   unpush(key) {
@@ -408,20 +415,24 @@ class LRU {
 /**
  * LRU Item
  * @alias module:utils.LRUItem
+ * @template K - Key type
+ * @template V - Value type
  */
 
 class LRUItem {
   /**
    * Create an LRU item.
    * @constructor
-   * @param {String|Number} key
-   * @param {Object} value
+   * @param {K} key
+   * @param {V} value
    */
 
   constructor(key, value) {
     this.key = key;
     this.value = value;
+    /** @type {LRUItem<K, V>?} */
     this.next = null;
+    /** @type {LRUItem<K, V>?} */
     this.prev = null;
   }
 }
@@ -429,24 +440,27 @@ class LRUItem {
 /**
  * LRU Batch
  * @alias module:utils.LRUBatch
+ * @template K - Key type
+ * @template V - Value type
  */
 
 class LRUBatch {
   /**
    * Create an LRU batch.
    * @constructor
-   * @param {LRU} lru
+   * @param {LRU<K, V>} lru
    */
 
   constructor(lru) {
     this.lru = lru;
+    /** @type {LRUOp<K, V>[]} */
     this.ops = [];
   }
 
   /**
    * Push an item onto the batch.
-   * @param {String} key
-   * @param {Object} value
+   * @param {K} key
+   * @param {V} value
    */
 
   set(key, value) {
@@ -455,7 +469,7 @@ class LRUBatch {
 
   /**
    * Push a removal onto the batch.
-   * @param {String} key
+   * @param {K} key
    */
 
   remove(key) {
@@ -490,6 +504,8 @@ class LRUBatch {
 /**
  * LRU Op
  * @alias module:utils.LRUOp
+ * @template K
+ * @template V
  * @private
  */
 
@@ -498,8 +514,8 @@ class LRUOp {
    * Create an LRU op.
    * @constructor
    * @param {Boolean} remove
-   * @param {String} key
-   * @param {Object} value
+   * @param {K} key
+   * @param {V} value
    */
 
   constructor(remove, key, value) {