diff --git a/packages/idempotency/src/IdempotencyHandler.ts b/packages/idempotency/src/IdempotencyHandler.ts
index aad48f9dea..c5d5e4ee6b 100644
--- a/packages/idempotency/src/IdempotencyHandler.ts
+++ b/packages/idempotency/src/IdempotencyHandler.ts
@@ -337,7 +337,7 @@ export class IdempotencyHandler<Func extends AnyFunction> {
    *
    * This is called when the handler throws an error.
    */
-  #deleteInProgressRecord = async (): Promise<void> => {
+  readonly #deleteInProgressRecord = async (): Promise<void> => {
     try {
       await this.#persistenceStore.deleteRecord(
         this.#functionPayloadToBeHashed
@@ -356,7 +356,7 @@ export class IdempotencyHandler<Func extends AnyFunction> {
    * Before returning a result, we might neede to look up the idempotency record
    * and validate it to ensure that it is consistent with the payload to be hashed.
    */
-  #saveInProgressOrReturnExistingResult = async (): Promise<{
+  readonly #saveInProgressOrReturnExistingResult = async (): Promise<{
     isIdempotent: boolean;
     result: JSONValue;
   }> => {
@@ -419,7 +419,9 @@ export class IdempotencyHandler<Func extends AnyFunction> {
    *
    * @param result The result returned by the handler.
    */
-  #saveSuccessfulResult = async (result: ReturnType<Func>): Promise<void> => {
+  readonly #saveSuccessfulResult = async (
+    result: ReturnType<Func>
+  ): Promise<void> => {
     try {
       await this.#persistenceStore.saveSuccess(
         this.#functionPayloadToBeHashed,
diff --git a/packages/idempotency/src/config/EnvironmentVariablesService.ts b/packages/idempotency/src/config/EnvironmentVariablesService.ts
index b5cc1ba262..36af2c4b4a 100644
--- a/packages/idempotency/src/config/EnvironmentVariablesService.ts
+++ b/packages/idempotency/src/config/EnvironmentVariablesService.ts
@@ -19,8 +19,9 @@ class EnvironmentVariablesService
   implements ConfigServiceInterface
 {
   // Reserved environment variables
-  private functionNameVariable = 'AWS_LAMBDA_FUNCTION_NAME';
-  private idempotencyDisabledVariable = 'POWERTOOLS_IDEMPOTENCY_DISABLED';
+  private readonly functionNameVariable = 'AWS_LAMBDA_FUNCTION_NAME';
+  private readonly idempotencyDisabledVariable =
+    'POWERTOOLS_IDEMPOTENCY_DISABLED';
 
   /**
    * It returns the value of the AWS_LAMBDA_FUNCTION_NAME environment variable.
diff --git a/packages/idempotency/src/persistence/BasePersistenceLayer.ts b/packages/idempotency/src/persistence/BasePersistenceLayer.ts
index 515a315652..2ca6690336 100644
--- a/packages/idempotency/src/persistence/BasePersistenceLayer.ts
+++ b/packages/idempotency/src/persistence/BasePersistenceLayer.ts
@@ -28,7 +28,7 @@ abstract class BasePersistenceLayer implements BasePersistenceLayerInterface {
   private cache?: LRUCache<string, IdempotencyRecord>;
   private configured = false;
   // envVarsService is always initialized in the constructor
-  private envVarsService!: EnvironmentVariablesService;
+  private readonly envVarsService!: EnvironmentVariablesService;
   private eventKeyJmesPath?: string;
   protected expiresAfterSeconds: number = 60 * 60; // 1 hour default
   private hashFunction = 'md5';
diff --git a/packages/idempotency/src/persistence/DynamoDBPersistenceLayer.ts b/packages/idempotency/src/persistence/DynamoDBPersistenceLayer.ts
index c9daed42e9..4e88f99b51 100644
--- a/packages/idempotency/src/persistence/DynamoDBPersistenceLayer.ts
+++ b/packages/idempotency/src/persistence/DynamoDBPersistenceLayer.ts
@@ -50,16 +50,16 @@ import { IdempotencyRecord } from './IdempotencyRecord.js';
  * @category Persistence Layer
  */
 class DynamoDBPersistenceLayer extends BasePersistenceLayer {
-  private client: DynamoDBClient;
-  private dataAttr: string;
-  private expiryAttr: string;
-  private inProgressExpiryAttr: string;
-  private keyAttr: string;
-  private sortKeyAttr?: string;
-  private staticPkValue: string;
-  private statusAttr: string;
-  private tableName: string;
-  private validationKeyAttr: string;
+  private readonly client: DynamoDBClient;
+  private readonly dataAttr: string;
+  private readonly expiryAttr: string;
+  private readonly inProgressExpiryAttr: string;
+  private readonly keyAttr: string;
+  private readonly sortKeyAttr?: string;
+  private readonly staticPkValue: string;
+  private readonly statusAttr: string;
+  private readonly tableName: string;
+  private readonly validationKeyAttr: string;
 
   public constructor(config: DynamoDBPersistenceOptions) {
     super();
diff --git a/packages/idempotency/src/persistence/IdempotencyRecord.ts b/packages/idempotency/src/persistence/IdempotencyRecord.ts
index 9d83a17bb8..e222554c85 100644
--- a/packages/idempotency/src/persistence/IdempotencyRecord.ts
+++ b/packages/idempotency/src/persistence/IdempotencyRecord.ts
@@ -42,7 +42,7 @@ class IdempotencyRecord {
    * {@link constants.IdempotencyRecordStatusValue | IdempotencyRecordStatusValue}
    * @private
    */
-  private status: IdempotencyRecordStatusValue;
+  private readonly status: IdempotencyRecordStatusValue;
 
   public constructor(config: IdempotencyRecordOptions) {
     this.idempotencyKey = config.idempotencyKey;