diff --git a/index.ts b/index.ts
index 5ccbdac..57ea503 100644
--- a/index.ts
+++ b/index.ts
@@ -35,7 +35,12 @@ export type IndexConfig = {
 /**
  * Serverless vector client for upstash.
  */
-export class Index extends core.Index {
+export class Index<
+  TIndexMetadata extends Record<
+    string,
+    unknown
+  > = Record<string, unknown>
+> extends core.Index<TIndexMetadata> {
   /**
    * Create a new vector client by providing the url and token
    *
diff --git a/src/commands/client/fetch/index.ts b/src/commands/client/fetch/index.ts
index 4847e28..68e9b31 100644
--- a/src/commands/client/fetch/index.ts
+++ b/src/commands/client/fetch/index.ts
@@ -9,7 +9,7 @@ type FetchCommandOptions = {
 export type FetchResult<TMetadata = Record<string, unknown>> = Vector<TMetadata> | null;
 
 export class FetchCommand<TMetadata> extends Command<FetchResult<TMetadata>[]> {
-  constructor([ids, opts]: [ids: number[] | string[], opts: FetchCommandOptions]) {
+  constructor([ids, opts]: [ids: number[] | string[], opts?: FetchCommandOptions]) {
     super({ ids, ...opts }, "fetch");
   }
 }
diff --git a/src/commands/client/upsert/index.ts b/src/commands/client/upsert/index.ts
index a320c61..ee28e0a 100644
--- a/src/commands/client/upsert/index.ts
+++ b/src/commands/client/upsert/index.ts
@@ -1,13 +1,13 @@
 import { Command } from "@commands/command";
 
-type UpsertCommandPayload = {
+type UpsertCommandPayload<TMetadata> = {
   id: number | string;
   vector: number[];
-  metadata?: Record<string, unknown>;
+  metadata?: TMetadata;
 };
 
-export class UpsertCommand extends Command<string> {
-  constructor(payload: UpsertCommandPayload | UpsertCommandPayload[]) {
+export class UpsertCommand<TMetadata> extends Command<string> {
+  constructor(payload: UpsertCommandPayload<TMetadata> | UpsertCommandPayload<TMetadata>[]) {
     super(payload, "upsert");
   }
 }
diff --git a/src/vector.ts b/src/vector.ts
index 42780db..466b1c4 100644
--- a/src/vector.ts
+++ b/src/vector.ts
@@ -15,7 +15,7 @@ export type CommandArgs<TCommand extends new (_args: any) => any> =
 /**
  * Serverless vector client for upstash vector db.
  */
-export class Index {
+export class Index<TIndexMetadata extends Record<string, unknown> = Record<string, unknown>> {
   protected client: Requester;
 
   /**
@@ -64,8 +64,9 @@ export class Index {
    *
    * @returns A promise that resolves with an array of query result objects when the request to query the index is completed.
    */
-  query = <TMetadata>(args: CommandArgs<typeof QueryCommand>) =>
-    new QueryCommand<TMetadata>(args).exec(this.client);
+  query = <TMetadata extends TIndexMetadata = TIndexMetadata>(
+    args: CommandArgs<typeof QueryCommand>
+  ) => new QueryCommand<TMetadata>(args).exec(this.client);
 
   /**
    * Upserts (Updates and Inserts) specific items into the index.
@@ -89,7 +90,9 @@ export class Index {
    *
    * @returns {string} A promise that resolves with the result of the upsert operation after the command is executed.
    */
-  upsert = (args: CommandArgs<typeof UpsertCommand>) => new UpsertCommand(args).exec(this.client);
+  upsert = <TMetadata extends TIndexMetadata = TIndexMetadata>(
+    args: CommandArgs<typeof UpsertCommand<TMetadata>>
+  ) => new UpsertCommand<TMetadata>(args).exec(this.client);
 
   /**
    * It's used for retrieving specific items from the index, optionally including
@@ -111,8 +114,9 @@ export class Index {
    *
    * @returns {Promise<FetchReturnResponse<TMetadata>[]>} A promise that resolves with an array of fetched items or null if not found, after the command is executed.
    */
-  fetch = <TMetadata>(...args: CommandArgs<typeof FetchCommand>) =>
-    new FetchCommand<TMetadata>(args).exec(this.client);
+  fetch = <TMetadata extends TIndexMetadata = TIndexMetadata>(
+    ...args: CommandArgs<typeof FetchCommand>
+  ) => new FetchCommand<TMetadata>(args).exec(this.client);
 
   /**
    * It's used for wiping an entire index.
@@ -150,8 +154,9 @@ export class Index {
    *
    * @returns {Promise<RangeReturnResponse<TMetadata>>} A promise that resolves with the response containing the next cursor and an array of vectors, after the command is executed.
    */
-  range = <TMetadata>(args: CommandArgs<typeof RangeCommand>) =>
-    new RangeCommand<TMetadata>(args).exec(this.client);
+  range = <TMetadata extends TIndexMetadata = TIndexMetadata>(
+    args: CommandArgs<typeof RangeCommand>
+  ) => new RangeCommand<TMetadata>(args).exec(this.client);
 
   /**
    * Retrieves info from the index.