diff --git a/src/commands/aws/parameterstore/list/list.ts b/src/commands/aws/parameterstore/list/list.ts
index 3461b1d..1f35223 100644
--- a/src/commands/aws/parameterstore/list/list.ts
+++ b/src/commands/aws/parameterstore/list/list.ts
@@ -1,6 +1,10 @@
 import { GluegunMenuToolbox } from '@lenne.tech/gluegun-menu';
 import chalk = require('chalk');
 import { defaultMenuSettings, sleep } from '../../../../globals';
+import {
+  readParameterNameCache,
+  writeParameterNameCache,
+} from '../../../../common/parameterstore-cache';
 const { AutoComplete } = require('enquirer');
 
 module.exports = {
@@ -9,12 +13,9 @@ module.exports = {
   description: 'List all parameters in parameter store (a ps l)',
   hidden: false,
   run: async (toolbox: GluegunMenuToolbox) => {
-    const { system, strings, print, filesystem } = toolbox;
+    const { system, strings, print } = toolbox;
 
-    // Check for cache in /tmp folder
-    const cache = filesystem.read('/tmp/.pwcli_parametercache');
-    const cacheValues = !cache ? [] : JSON.parse(cache);
-    const valueNames = [...cacheValues];
+    const valueNames = [...readParameterNameCache(toolbox)];
 
     let nextToken = '';
     if (valueNames.length === 0) {
@@ -45,11 +46,7 @@ module.exports = {
       }
 
       spinner.text = 'Saving parameter names to /tmp/.pwcli_parametercache';
-
-      filesystem.file('/tmp/.pwcli_parametercache', {
-        mode: '600',
-        content: JSON.stringify(valueNames),
-      });
+      writeParameterNameCache(toolbox, valueNames);
       await sleep(2000);
 
       spinner.stop();
diff --git a/src/commands/aws/parameterstore/update/update.ts b/src/commands/aws/parameterstore/update/update.ts
index 0ba60dc..ed99d08 100644
--- a/src/commands/aws/parameterstore/update/update.ts
+++ b/src/commands/aws/parameterstore/update/update.ts
@@ -1,7 +1,10 @@
 import { GluegunMenuToolbox } from '@lenne.tech/gluegun-menu';
 import chalk = require('chalk');
 import { defaultMenuSettings, sleep } from '../../../../globals';
-import * as fs from 'fs';
+import {
+  parameterNameCacheFilePath,
+  readParameterNameCache,
+} from '../../../../common/parameterstore-cache';
 const { AutoComplete } = require('enquirer');
 
 module.exports = {
@@ -10,18 +13,13 @@ module.exports = {
   description: 'Update an existing item in parameter store (a ps u)',
   hidden: false,
   run: async (toolbox: GluegunMenuToolbox) => {
-    const { print, prompt, system, filesystem } = toolbox;
+    const { print, prompt, system } = toolbox;
 
-    // Read the .pwcli_parametercache file
-    const cacheFilePath = '/tmp/.pwcli_parametercache';
-    let parameters = [];
-    if (fs.existsSync(cacheFilePath)) {
-      const cacheContent = await filesystem.read(cacheFilePath);
-      parameters = JSON.parse(cacheContent);
-    } else {
+    const parameters = readParameterNameCache(toolbox);
+    if (parameters.length === 0) {
       print.error(
         chalk.red(
-          'Cache file not found. Please run "a ps l" first to populate the cache.',
+          `Parameter name cache is missing or invalid at "${parameterNameCacheFilePath}". Run "a ps l" to populate a name-only cache.`,
         ),
       );
       return;
diff --git a/src/common/parameterstore-cache.ts b/src/common/parameterstore-cache.ts
new file mode 100644
index 0000000..6015aa9
--- /dev/null
+++ b/src/common/parameterstore-cache.ts
@@ -0,0 +1,37 @@
+import { GluegunMenuToolbox } from '@lenne.tech/gluegun-menu';
+
+export const parameterNameCacheFilePath = '/tmp/.pwcli_parametercache';
+
+const isParameterNameList = (value: unknown): value is string[] => {
+  return (
+    Array.isArray(value) && value.every((item) => typeof item === 'string')
+  );
+};
+
+export const readParameterNameCache = (
+  toolbox: GluegunMenuToolbox,
+): string[] => {
+  const { filesystem } = toolbox;
+  const cache = filesystem.read(parameterNameCacheFilePath);
+
+  if (!cache) {
+    return [];
+  }
+
+  try {
+    const parsedCache = JSON.parse(cache);
+    return isParameterNameList(parsedCache) ? parsedCache : [];
+  } catch {
+    return [];
+  }
+};
+
+export const writeParameterNameCache = (
+  toolbox: GluegunMenuToolbox,
+  parameterNames: string[],
+) => {
+  toolbox.filesystem.file(parameterNameCacheFilePath, {
+    mode: '600',
+    content: JSON.stringify(parameterNames),
+  });
+};