diff --git a/bun.lockb b/bun.lockb
index 98a9e9d..d0edba9 100755
Binary files a/bun.lockb and b/bun.lockb differ
diff --git a/index.ts b/index.ts
index 3844a68..9e09b8a 100644
--- a/index.ts
+++ b/index.ts
@@ -1,2 +1,3 @@
 export * from "./src/rag-chat";
 export * from "./src/services/history";
+export * from "./src/error";
diff --git a/package.json b/package.json
index 2d1d403..6f2d9db 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@upstash/rag-chat",
-  "version": "0.0.11-alpha",
+  "version": "0.0.14-alpha",
   "main": "./dist/index.js",
   "module": "./dist/index.mjs",
   "types": "./dist/index.d.ts",
@@ -51,7 +51,7 @@
     "@langchain/community": "^0.0.50",
     "@langchain/core": "^0.1.58",
     "@langchain/openai": "^0.0.28",
-    "@upstash/sdk": "0.0.25-alpha",
+    "@upstash/sdk": "0.0.26-alpha",
     "ai": "^3.0.35"
   }
 }
diff --git a/src/clients/redis/index.test.ts b/src/clients/redis/index.test.ts
index d6f3542..394a239 100644
--- a/src/clients/redis/index.test.ts
+++ b/src/clients/redis/index.test.ts
@@ -1,7 +1,8 @@
 /* eslint-disable @typescript-eslint/no-non-null-assertion */
 import { Upstash } from "@upstash/sdk";
 import { describe, expect, test } from "bun:test";
-import { DEFAULT_REDIS_CONFIG, DEFAULT_REDIS_DB_NAME, RedisClient } from ".";
+import { DEFAULT_REDIS_CONFIG, RedisClient } from ".";
+import { DEFAULT_REDIS_DB_NAME } from "../../constants";
 
 const upstashSDK = new Upstash({
   email: process.env.UPSTASH_EMAIL!,
diff --git a/src/clients/redis/index.ts b/src/clients/redis/index.ts
index d78dc39..1a2cabf 100644
--- a/src/clients/redis/index.ts
+++ b/src/clients/redis/index.ts
@@ -2,8 +2,7 @@ import type { CreateCommandPayload, Upstash } from "@upstash/sdk";
 
 import { Redis } from "@upstash/sdk";
 import type { PreferredRegions } from "../../types";
-
-export const DEFAULT_REDIS_DB_NAME = "upstash-rag-chat-redis";
+import { DEFAULT_REDIS_DB_NAME } from "../../constants";
 
 export const DEFAULT_REDIS_CONFIG: CreateCommandPayload = {
   name: DEFAULT_REDIS_DB_NAME,
diff --git a/src/clients/vector/index.test.ts b/src/clients/vector/index.test.ts
index 4454c49..9819c3c 100644
--- a/src/clients/vector/index.test.ts
+++ b/src/clients/vector/index.test.ts
@@ -1,7 +1,8 @@
 /* eslint-disable @typescript-eslint/no-non-null-assertion */
 import { Upstash } from "@upstash/sdk";
 import { describe, expect, test } from "bun:test";
-import { DEFAULT_VECTOR_DB_NAME, VectorClient, DEFAULT_VECTOR_CONFIG } from ".";
+import { VectorClient, DEFAULT_VECTOR_CONFIG } from ".";
+import { DEFAULT_VECTOR_DB_NAME } from "../../constants";
 
 const upstashSDK = new Upstash({
   email: process.env.UPSTASH_EMAIL!,
diff --git a/src/clients/vector/index.ts b/src/clients/vector/index.ts
index 7c475bf..31d88e6 100644
--- a/src/clients/vector/index.ts
+++ b/src/clients/vector/index.ts
@@ -2,8 +2,7 @@ import type { CreateIndexPayload, Upstash } from "@upstash/sdk";
 import { Index } from "@upstash/sdk";
 
 import type { PreferredRegions } from "../../types";
-
-export const DEFAULT_VECTOR_DB_NAME = "upstash-rag-chat-vector";
+import { DEFAULT_VECTOR_DB_NAME } from "../../constants";
 
 export const DEFAULT_VECTOR_CONFIG: CreateIndexPayload = {
   name: DEFAULT_VECTOR_DB_NAME,
diff --git a/src/config.test.ts b/src/config.test.ts
index 7fc3493..05a4c35 100644
--- a/src/config.test.ts
+++ b/src/config.test.ts
@@ -3,7 +3,8 @@ import { PromptTemplate } from "@langchain/core/prompts";
 import { ChatOpenAI } from "@langchain/openai";
 import { Index, Redis } from "@upstash/sdk";
 import { expect, test } from "bun:test";
-import { Config, DEFAULT_REDIS_DB_NAME, DEFAULT_VECTOR_DB_NAME } from "./config";
+import { Config } from "./config";
+import { DEFAULT_VECTOR_DB_NAME, DEFAULT_REDIS_DB_NAME } from "./constants";
 
 const mockRedis = new Redis({
   token: "hey",
diff --git a/src/config.ts b/src/config.ts
index d145472..d0b1175 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -1,32 +1,20 @@
 import type { BaseLanguageModelInterface } from "@langchain/core/language_models/base";
 import type { PromptTemplate } from "@langchain/core/prompts";
+import type { Ratelimit } from "@upstash/sdk";
 import { Redis } from "@upstash/sdk";
 import { Index } from "@upstash/sdk";
-import type { PreferredRegions } from "./types";
-
-type RAGChatConfigCommon = {
-  model?: BaseLanguageModelInterface;
-  template?: PromptTemplate;
-  region?: PreferredRegions;
-};
-
-const PREFERRED_REGION: PreferredRegions = "us-east-1";
-export const DEFAULT_VECTOR_DB_NAME = "upstash-rag-chat-vector";
-export const DEFAULT_REDIS_DB_NAME = "upstash-rag-chat-redis";
-
-export type RAGChatConfig = {
-  vector?: string | Index;
-  redis?: string | Redis;
-} & RAGChatConfigCommon;
+import type { PreferredRegions, RAGChatConfig } from "./types";
+import { DEFAULT_REDIS_DB_NAME, DEFAULT_VECTOR_DB_NAME, PREFERRED_REGION } from "./constants";
 
 export class Config {
   public readonly token: string;
   public readonly email: string;
 
-  public readonly region: PreferredRegions;
   public readonly vector?: string | Index;
   public readonly redis?: string | Redis;
+  public readonly ratelimit?: Ratelimit;
 
+  public readonly region: PreferredRegions;
   public readonly model?: BaseLanguageModelInterface;
   public readonly template?: PromptTemplate;
 
@@ -45,6 +33,8 @@ export class Config {
         ? config.redis
         : DEFAULT_REDIS_DB_NAME;
 
+    this.ratelimit = config?.ratelimit;
+
     this.model = config?.model;
     this.template = config?.template;
   }
diff --git a/src/constants.ts b/src/constants.ts
new file mode 100644
index 0000000..cd9c7b9
--- /dev/null
+++ b/src/constants.ts
@@ -0,0 +1,10 @@
+import type { PreferredRegions } from "./types";
+
+export const DEFAULT_CHAT_SESSION_ID = "upstash-rag-chat-session";
+export const DEFAULT_CHAT_RATELIMIT_SESSION_ID = "upstash-rag-chat-ratelimit-session";
+
+export const RATELIMIT_ERROR_MESSAGE = "ERR:USER_RATELIMITED";
+
+export const DEFAULT_VECTOR_DB_NAME = "upstash-rag-chat-vector";
+export const DEFAULT_REDIS_DB_NAME = "upstash-rag-chat-redis";
+export const PREFERRED_REGION: PreferredRegions = "us-east-1";
diff --git a/src/error/index.ts b/src/error/index.ts
new file mode 100644
index 0000000..c42f9bc
--- /dev/null
+++ b/src/error/index.ts
@@ -0,0 +1 @@
+export * from "./ratelimit";
diff --git a/src/error/internal.ts b/src/error/internal.ts
index b115f3c..7a7f338 100644
--- a/src/error/internal.ts
+++ b/src/error/internal.ts
@@ -1,6 +1,6 @@
 export class InternalUpstashError extends Error {
   constructor(message: string) {
     super(message);
-    this.name = "InternalUpstashError";
+    this.name = "InternalError";
   }
 }
diff --git a/src/error/model.ts b/src/error/model.ts
index 179966f..aa19ed1 100644
--- a/src/error/model.ts
+++ b/src/error/model.ts
@@ -1,6 +1,6 @@
 export class UpstashModelError extends Error {
   constructor(message: string) {
     super(message);
-    this.name = "UpstashModelError";
+    this.name = "ModelError";
   }
 }
diff --git a/src/error/ratelimit.ts b/src/error/ratelimit.ts
new file mode 100644
index 0000000..567f7e7
--- /dev/null
+++ b/src/error/ratelimit.ts
@@ -0,0 +1,14 @@
+import type { RATELIMIT_ERROR_MESSAGE } from "../constants";
+
+type RatelimitResponse = {
+  error: typeof RATELIMIT_ERROR_MESSAGE;
+  resetTime?: number;
+};
+
+export class RatelimitUpstashError extends Error {
+  constructor(message: string, cause: RatelimitResponse) {
+    super(message);
+    this.name = "RatelimitError";
+    this.cause = cause;
+  }
+}
diff --git a/src/rag-chat.ts b/src/rag-chat.ts
index d7a6ec3..6efcd62 100644
--- a/src/rag-chat.ts
+++ b/src/rag-chat.ts
@@ -3,7 +3,7 @@ import type { BaseMessage } from "@langchain/core/messages";
 import { RunnableSequence, RunnableWithMessageHistory } from "@langchain/core/runnables";
 import { LangChainStream, StreamingTextResponse } from "ai";
 
-import { formatChatHistory, sanitizeQuestion } from "./utils";
+import { appendDefaultsIfNeeded, formatChatHistory, sanitizeQuestion } from "./utils";
 
 import type { BaseLanguageModelInterface } from "@langchain/core/language_models/base";
 import type { PromptTemplate } from "@langchain/core/prompts";
@@ -13,24 +13,16 @@ import { HistoryService } from "./services/history";
 import { RetrievalService } from "./services/retrieval";
 import { QA_TEMPLATE } from "./prompts";
 import { UpstashModelError } from "./error/model";
+import { RateLimitService } from "./services/ratelimit";
+import type { ChatOptions, PrepareChatResult, RAGChatConfig } from "./types";
+import { RatelimitUpstashError } from "./error/ratelimit";
 
 type CustomInputValues = { chat_history?: BaseMessage[]; question: string; context: string };
 
-type ChatOptions = {
-  stream: boolean;
-  sessionId: string;
-  includeHistory?: number;
-  similarityThreshold?: number;
-};
-
-type PrepareChatResult = {
-  question: string;
-  facts: string;
-};
-
 export class RAGChat {
   private retrievalService: RetrievalService;
   private historyService: HistoryService;
+  private ratelimitService: RateLimitService;
 
   private model: BaseLanguageModelInterface;
   private template: PromptTemplate;
@@ -38,10 +30,12 @@ export class RAGChat {
   constructor(
     retrievalService: RetrievalService,
     historyService: HistoryService,
+    ratelimitService: RateLimitService,
     config: { model: BaseLanguageModelInterface; template: PromptTemplate }
   ) {
     this.retrievalService = retrievalService;
     this.historyService = historyService;
+    this.ratelimitService = ratelimitService;
 
     this.model = config.model;
     this.template = config.template;
@@ -56,18 +50,33 @@ export class RAGChat {
     return { question, facts };
   }
 
-  async chat(input: string, options: ChatOptions) {
+  async chat(
+    input: string,
+    options: ChatOptions
+  ): Promise<StreamingTextResponse | Record<string, unknown>> {
+    const options_ = appendDefaultsIfNeeded(options);
+    const { success, resetTime } = await this.ratelimitService.checkLimit(
+      options_.ratelimitSessionId
+    );
+
+    if (!success) {
+      throw new RatelimitUpstashError("Couldn't process chat due to ratelimit.", {
+        error: "ERR:USER_RATELIMITED",
+        resetTime: resetTime,
+      });
+    }
+
     const { question, facts } = await this.prepareChat(input, options.similarityThreshold);
 
     return options.stream
-      ? this.streamingChainCall(question, facts, options)
-      : this.chainCall(options, question, facts);
+      ? this.streamingChainCall(options_, question, facts)
+      : this.chainCall(options_, question, facts);
   }
 
   private streamingChainCall = (
+    chatOptions: ChatOptions,
     question: string,
-    facts: string,
-    chatOptions: ChatOptions
+    facts: string
   ): StreamingTextResponse => {
     const { stream, handlers } = LangChainStream();
     void this.chainCall(chatOptions, question, facts, [handlers]);
@@ -75,7 +84,7 @@ export class RAGChat {
   };
 
   private chainCall(
-    chatOptions: { sessionId: string; includeHistory?: number },
+    chatOptions: ChatOptions,
     question: string,
     facts: string,
     handlers?: Callbacks
@@ -113,7 +122,9 @@ export class RAGChat {
     );
   }
 
-  static async initialize(config: Config): Promise<RAGChat> {
+  static async initialize(
+    config: RAGChatConfig & { email: string; token: string }
+  ): Promise<RAGChat> {
     const clientFactory = new ClientFactory(
       new Config(config.email, config.token, {
         redis: config.redis,
@@ -125,12 +136,13 @@ export class RAGChat {
 
     const historyService = new HistoryService(redis);
     const retrievalService = new RetrievalService(index);
+    const ratelimitService = new RateLimitService(config.ratelimit);
 
     if (!config.model) {
       throw new UpstashModelError("Model can not be undefined!");
     }
 
-    return new RAGChat(retrievalService, historyService, {
+    return new RAGChat(retrievalService, historyService, ratelimitService, {
       model: config.model,
       template: config.template ?? QA_TEMPLATE,
     });
diff --git a/src/services/history.ts b/src/services/history.ts
index c541591..d876eab 100644
--- a/src/services/history.ts
+++ b/src/services/history.ts
@@ -1,8 +1,8 @@
 import type { Redis } from "@upstash/sdk";
 import { CustomUpstashRedisChatMessageHistory } from "./redis-custom-history";
-import type { RAGChatConfig } from "../config";
 import { Config } from "../config";
 import { ClientFactory } from "../client-factory";
+import type { RAGChatConfig } from "../types";
 
 const DAY_IN_SECONDS = 86_400;
 const TOP_6 = 5;
diff --git a/src/services/ratelimit.ts b/src/services/ratelimit.ts
new file mode 100644
index 0000000..ca131b3
--- /dev/null
+++ b/src/services/ratelimit.ts
@@ -0,0 +1,22 @@
+import type { Ratelimit } from "@upstash/sdk";
+
+export class RateLimitService {
+  private ratelimit?: Ratelimit;
+
+  constructor(ratelimit?: Ratelimit) {
+    this.ratelimit = ratelimit;
+  }
+
+  async checkLimit(sessionId: string): Promise<{ success: boolean; resetTime?: number }> {
+    if (!this.ratelimit) {
+      // If no ratelimit object is provided, always allow the operation.
+      return { success: true };
+    }
+
+    const result = await this.ratelimit.limit(sessionId);
+    if (!result.success) {
+      return { success: false, resetTime: result.reset };
+    }
+    return { success: true };
+  }
+}
diff --git a/src/types.ts b/src/types.ts
index c0e75f8..bc4a451 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1 +1,30 @@
+import type { BaseLanguageModelInterface } from "@langchain/core/language_models/base";
+import type { PromptTemplate } from "@langchain/core/prompts";
+import type { Index, Ratelimit, Redis } from "@upstash/sdk";
+
 export type PreferredRegions = "eu-west-1" | "us-east-1";
+
+export type ChatOptions = {
+  stream: boolean;
+  sessionId?: string;
+  includeHistory?: number;
+  similarityThreshold?: number;
+  ratelimitSessionId?: string;
+};
+
+export type PrepareChatResult = {
+  question: string;
+  facts: string;
+};
+
+type RAGChatConfigCommon = {
+  model?: BaseLanguageModelInterface;
+  template?: PromptTemplate;
+  region?: PreferredRegions;
+  ratelimit?: Ratelimit;
+};
+
+export type RAGChatConfig = {
+  vector?: string | Index;
+  redis?: string | Redis;
+} & RAGChatConfigCommon;
diff --git a/src/utils.ts b/src/utils.ts
index 3c5ac68..2a3a624 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -1,4 +1,6 @@
 import type { BaseMessage } from "@langchain/core/messages";
+import type { ChatOptions } from "./types";
+import { DEFAULT_CHAT_SESSION_ID, DEFAULT_CHAT_RATELIMIT_SESSION_ID } from "./constants";
 
 export const sanitizeQuestion = (question: string) => {
   return question.trim().replaceAll("\n", " ");
@@ -17,3 +19,11 @@ export const formatChatHistory = (chatHistory: BaseMessage[]) => {
 
   return formatFacts(formattedDialogueTurns);
 };
+
+export function appendDefaultsIfNeeded(options: ChatOptions) {
+  return {
+    ...options,
+    sessionId: options.sessionId ?? DEFAULT_CHAT_SESSION_ID,
+    ratelimitSessionId: options.ratelimitSessionId ?? DEFAULT_CHAT_RATELIMIT_SESSION_ID,
+  } satisfies ChatOptions;
+}