diff --git a/packages/analytics-remote-config/src/remote-config.ts b/packages/analytics-remote-config/src/remote-config.ts
index 02fc0bd9c..c6ee48c07 100644
--- a/packages/analytics-remote-config/src/remote-config.ts
+++ b/packages/analytics-remote-config/src/remote-config.ts
@@ -23,7 +23,7 @@ export class RemoteConfigFetch<RemoteConfig extends { [key: string]: object }>
   localConfig: Config;
   retryTimeout = 1000;
   attempts = 0;
-  lastFetchedSessionId: number | string | undefined;
+  lastFetchedSessionId: number | undefined;
   sessionTargetingMatch = false;
   configKeys: string[];
   metrics: RemoteConfigMetric = {};
@@ -36,7 +36,7 @@ export class RemoteConfigFetch<RemoteConfig extends { [key: string]: object }>
   getRemoteConfig = async <K extends keyof RemoteConfig>(
     configNamespace: string,
     key: K,
-    sessionId?: number | string,
+    sessionId?: number,
   ): Promise<RemoteConfig[K] | undefined> => {
     const fetchStartTime = Date.now();
     // Finally fetch via API
@@ -64,7 +64,7 @@ export class RemoteConfigFetch<RemoteConfig extends { [key: string]: object }>
     return REMOTE_CONFIG_SERVER_URL;
   }
 
-  fetchWithTimeout = async (sessionId?: number | string): Promise<RemoteConfigAPIResponse<RemoteConfig> | void> => {
+  fetchWithTimeout = async (sessionId?: number): Promise<RemoteConfigAPIResponse<RemoteConfig> | void> => {
     const controller = new AbortController();
     const timeoutId = setTimeout(() => controller.abort(), 5000);
     const remoteConfig = await this.fetchRemoteConfig(controller.signal, sessionId);
@@ -74,7 +74,7 @@ export class RemoteConfigFetch<RemoteConfig extends { [key: string]: object }>
 
   fetchRemoteConfig = async (
     signal: AbortController['signal'],
-    sessionId?: number | string,
+    sessionId?: number,
   ): Promise<RemoteConfigAPIResponse<RemoteConfig> | void> => {
     if (sessionId === this.lastFetchedSessionId && this.attempts >= this.localConfig.flushMaxRetries) {
       return this.completeRequest({ err: MAX_RETRIES_EXCEEDED_MESSAGE });
@@ -128,7 +128,7 @@ export class RemoteConfigFetch<RemoteConfig extends { [key: string]: object }>
 
   retryFetch = async (
     signal: AbortController['signal'],
-    sessionId?: number | string,
+    sessionId?: number,
   ): Promise<RemoteConfigAPIResponse<RemoteConfig> | void> => {
     await new Promise((resolve) => setTimeout(resolve, this.attempts * this.retryTimeout));
     return this.fetchRemoteConfig(signal, sessionId);
diff --git a/packages/analytics-remote-config/src/types.ts b/packages/analytics-remote-config/src/types.ts
index f0591d261..4e7e841e0 100644
--- a/packages/analytics-remote-config/src/types.ts
+++ b/packages/analytics-remote-config/src/types.ts
@@ -10,7 +10,7 @@ export interface BaseRemoteConfigFetch<T> {
   getRemoteConfig: <K extends keyof T>(
     configNamespace: string,
     key: K,
-    sessionId?: number | string,
+    sessionId?: number,
   ) => Promise<T[K] | undefined>;
 }
 
diff --git a/packages/plugin-session-replay-browser/src/session-replay.ts b/packages/plugin-session-replay-browser/src/session-replay.ts
index 85604f2d8..e33f78477 100644
--- a/packages/plugin-session-replay-browser/src/session-replay.ts
+++ b/packages/plugin-session-replay-browser/src/session-replay.ts
@@ -48,7 +48,7 @@ export class SessionReplayPlugin implements EnrichmentPlugin {
         instanceName: this.config.instanceName,
         deviceId: this.config.deviceId,
         optOut: this.config.optOut,
-        sessionId: this.options.customSessionId ? undefined : this.config.sessionId,
+        sessionId: this.config.sessionId,
         loggerProvider: this.config.loggerProvider,
         logLevel: this.config.logLevel,
         flushMaxRetries: this.config.flushMaxRetries,
@@ -74,41 +74,21 @@ export class SessionReplayPlugin implements EnrichmentPlugin {
 
   async execute(event: Event) {
     try {
-      if (this.options.customSessionId) {
-        const sessionId = this.options.customSessionId(event);
-        if (sessionId) {
-          // On event, synchronize the session id to the custom session id from the event. This may
-          // suffer from offline/delayed events messing up the state stored
-          if (sessionId !== sessionReplay.getSessionId()) {
-            await sessionReplay.setSessionId(sessionId).promise;
-          }
-
-          const sessionRecordingProperties = sessionReplay.getSessionReplayProperties();
-          event.event_properties = {
-            ...event.event_properties,
-            ...sessionRecordingProperties,
-          };
-        }
-      } else {
-        // On event, synchronize the session id to the what's on the browserConfig (source of truth)
-        // Choosing not to read from event object here, concerned about offline/delayed events messing up the state stored
-        // in SR.
-        const sessionId: string | number | undefined = this.config.sessionId;
-        if (sessionId && sessionId !== sessionReplay.getSessionId()) {
-          await sessionReplay.setSessionId(sessionId).promise;
-        }
-
-        // Treating config.sessionId as source of truth, if the event's session id doesn't match, the
-        // event is not of the current session (offline/late events). In that case, don't tag the events
-        if (sessionId && sessionId === event.session_id) {
-          const sessionRecordingProperties = sessionReplay.getSessionReplayProperties();
-          event.event_properties = {
-            ...event.event_properties,
-            ...sessionRecordingProperties,
-          };
-        }
+      // On event, synchronize the session id to the what's on the browserConfig (source of truth)
+      // Choosing not to read from event object here, concerned about offline/delayed events messing up the state stored
+      // in SR.
+      if (this.config.sessionId && this.config.sessionId !== sessionReplay.getSessionId()) {
+        await sessionReplay.setSessionId(this.config.sessionId).promise;
+      }
+      // Treating config.sessionId as source of truth, if the event's session id doesn't match, the
+      // event is not of the current session (offline/late events). In that case, don't tag the events
+      if (this.config.sessionId && this.config.sessionId === event.session_id) {
+        const sessionRecordingProperties = sessionReplay.getSessionReplayProperties();
+        event.event_properties = {
+          ...event.event_properties,
+          ...sessionRecordingProperties,
+        };
       }
-
       return Promise.resolve(event);
     } catch (error) {
       this.config.loggerProvider.error(`Session Replay: Failed to enrich event due to ${(error as Error).message}`);
diff --git a/packages/plugin-session-replay-browser/src/typings/session-replay.ts b/packages/plugin-session-replay-browser/src/typings/session-replay.ts
index 7a58e7c0e..317baa1a6 100644
--- a/packages/plugin-session-replay-browser/src/typings/session-replay.ts
+++ b/packages/plugin-session-replay-browser/src/typings/session-replay.ts
@@ -1,4 +1,3 @@
-import { Event } from '@amplitude/analytics-types';
 import { StoreType } from '@amplitude/session-replay-browser';
 
 export type MaskLevel =
@@ -27,5 +26,4 @@ export interface SessionReplayOptions {
   shouldInlineStylesheet?: boolean;
   performanceConfig?: SessionReplayPerformanceConfig;
   storeType?: StoreType;
-  customSessionId?: (event: Event) => string | undefined;
 }
diff --git a/packages/plugin-session-replay-browser/test/session-replay.test.ts b/packages/plugin-session-replay-browser/test/session-replay.test.ts
index e7101fa05..49437fbd7 100644
--- a/packages/plugin-session-replay-browser/test/session-replay.test.ts
+++ b/packages/plugin-session-replay-browser/test/session-replay.test.ts
@@ -1,4 +1,4 @@
-import { BrowserClient, BrowserConfig, LogLevel, Logger, Plugin, Event } from '@amplitude/analytics-types';
+import { BrowserClient, BrowserConfig, LogLevel, Logger, Plugin } from '@amplitude/analytics-types';
 import * as sessionReplayBrowser from '@amplitude/session-replay-browser';
 import { SessionReplayPlugin, sessionReplayPlugin } from '../src/session-replay';
 import { VERSION } from '../src/version';
@@ -304,84 +304,6 @@ describe('SessionReplayPlugin', () => {
       });
       await sessionReplay.teardown?.();
     });
-
-    test('should update the session id on any event when using custom session id', async () => {
-      const sessionReplay = sessionReplayPlugin({
-        customSessionId: (event: Event) => {
-          const event_properties = event.event_properties as { [key: string]: any };
-          if (!event_properties) {
-            return;
-          }
-          return event_properties['custom_session_id'] as string | undefined;
-        },
-      });
-      await sessionReplay.setup({ ...mockConfig });
-      getSessionId.mockReturnValueOnce('test_122');
-      const event = {
-        event_type: 'event_type',
-        event_properties: {
-          property_a: true,
-          property_b: 123,
-          custom_session_id: 'test_123',
-        },
-        session_id: 124,
-      };
-
-      await sessionReplay.execute(event);
-      expect(setSessionId).toHaveBeenCalledTimes(1);
-      expect(setSessionId).toHaveBeenCalledWith('test_123');
-    });
-
-    test('should not update the session id when using custom session id and it does not change', async () => {
-      const sessionReplay = sessionReplayPlugin({
-        customSessionId: (event: Event) => {
-          const event_properties = event.event_properties as { [key: string]: any };
-          if (!event_properties) {
-            return;
-          }
-          return event_properties['custom_session_id'] as string | undefined;
-        },
-      });
-      await sessionReplay.setup({ ...mockConfig });
-      getSessionId.mockReturnValueOnce('test_123');
-      const event = {
-        event_type: 'event_type',
-        event_properties: {
-          property_a: true,
-          property_b: 123,
-          custom_session_id: 'test_123',
-        },
-        session_id: 124,
-      };
-
-      await sessionReplay.execute(event);
-      expect(setSessionId).not.toHaveBeenCalled();
-    });
-
-    test('should do nothing when the custom session id cannot be found', async () => {
-      const sessionReplay = sessionReplayPlugin({
-        customSessionId: (event: Event) => {
-          const event_properties = event.event_properties as { [key: string]: any };
-          if (!event_properties) {
-            return;
-          }
-          return event_properties['custom_session_id'] as string | undefined;
-        },
-      });
-      await sessionReplay.setup({ ...mockConfig });
-      const event = {
-        event_type: 'event_type',
-        event_properties: {
-          property_a: true,
-          property_b: 123,
-        },
-        session_id: 124,
-      };
-
-      const enrichedEvent = await sessionReplay.execute(event);
-      expect(setSessionId).not.toHaveBeenCalled();
-      expect(enrichedEvent).toEqual(event);
-    });
   });
 
   describe('getSessionReplayProperties', () => {
diff --git a/packages/session-replay-browser/src/config/joined-config.ts b/packages/session-replay-browser/src/config/joined-config.ts
index 7c74d2d05..19554d66b 100644
--- a/packages/session-replay-browser/src/config/joined-config.ts
+++ b/packages/session-replay-browser/src/config/joined-config.ts
@@ -46,7 +46,7 @@ export class SessionReplayJoinedConfigGenerator {
     this.remoteConfigFetch = remoteConfigFetch;
   }
 
-  async generateJoinedConfig(sessionId?: string | number): Promise<SessionReplayJoinedConfig> {
+  async generateJoinedConfig(sessionId?: number): Promise<SessionReplayJoinedConfig> {
     const config: SessionReplayJoinedConfig = { ...this.localConfig };
     // Special case here as optOut is implemented via getter/setter
     config.optOut = this.localConfig.optOut;
diff --git a/packages/session-replay-browser/src/config/types.ts b/packages/session-replay-browser/src/config/types.ts
index 55f602379..ed22ba448 100644
--- a/packages/session-replay-browser/src/config/types.ts
+++ b/packages/session-replay-browser/src/config/types.ts
@@ -67,7 +67,7 @@ export interface SessionReplayRemoteConfigFetch {
 }
 
 export interface SessionReplayJoinedConfigGenerator {
-  generateJoinedConfig: (sessionId?: string | number) => Promise<SessionReplayJoinedConfig>;
+  generateJoinedConfig: (sessionId?: number) => Promise<SessionReplayJoinedConfig>;
 }
 
 export interface SessionReplayVersion {
diff --git a/packages/session-replay-browser/src/events/base-events-store.ts b/packages/session-replay-browser/src/events/base-events-store.ts
index 44cfb5cfc..8f22c9cda 100644
--- a/packages/session-replay-browser/src/events/base-events-store.ts
+++ b/packages/session-replay-browser/src/events/base-events-store.ts
@@ -29,12 +29,12 @@ export abstract class BaseEventsStore<KeyType> implements EventsStore<KeyType> {
   }
 
   abstract addEventToCurrentSequence(
-    sessionId: string | number,
+    sessionId: number,
     event: string,
   ): Promise<SendingSequencesReturn<KeyType> | undefined>;
   abstract getSequencesToSend(): Promise<SendingSequencesReturn<KeyType>[] | undefined>;
   abstract storeCurrentSequence(sessionId: number): Promise<SendingSequencesReturn<KeyType> | undefined>;
-  abstract storeSendingEvents(sessionId: string | number, events: Events): Promise<KeyType | undefined>;
+  abstract storeSendingEvents(sessionId: number, events: Events): Promise<KeyType | undefined>;
   abstract cleanUpSessionEventsStore(sessionId: number, sequenceId: KeyType): Promise<void>;
 
   /**
diff --git a/packages/session-replay-browser/src/events/event-compressor.ts b/packages/session-replay-browser/src/events/event-compressor.ts
index 600e73356..4581ec023 100644
--- a/packages/session-replay-browser/src/events/event-compressor.ts
+++ b/packages/session-replay-browser/src/events/event-compressor.ts
@@ -6,7 +6,7 @@ import { getGlobalScope } from '@amplitude/analytics-client-common';
 
 interface TaskQueue {
   event: eventWithTime;
-  sessionId: string | number;
+  sessionId: number;
 }
 
 const DEFAULT_TIMEOUT = 2000;
@@ -46,7 +46,7 @@ export class EventCompressor {
   }
 
   // Add an event to the task queue if idle callback is supported or compress the event directly
-  public enqueueEvent(event: eventWithTime, sessionId: string | number): void {
+  public enqueueEvent(event: eventWithTime, sessionId: number): void {
     if (this.canUseIdleCallback && this.config.performanceConfig?.enabled) {
       this.config.loggerProvider.debug('Enqueuing event for processing during idle time.');
       this.taskQueue.push({ event, sessionId });
@@ -86,7 +86,7 @@ export class EventCompressor {
     return JSON.stringify(packedEvent);
   };
 
-  public addCompressedEvent = (event: eventWithTime, sessionId: string | number) => {
+  public addCompressedEvent = (event: eventWithTime, sessionId: number) => {
     const compressedEvent = this.compressEvent(event);
 
     if (this.eventsManager && this.deviceId) {
diff --git a/packages/session-replay-browser/src/events/events-idb-store.ts b/packages/session-replay-browser/src/events/events-idb-store.ts
index 38e03451d..558156b10 100644
--- a/packages/session-replay-browser/src/events/events-idb-store.ts
+++ b/packages/session-replay-browser/src/events/events-idb-store.ts
@@ -18,7 +18,7 @@ export interface SessionReplayDB extends DBSchema {
   sequencesToSend: {
     key: number;
     value: Omit<SendingSequencesReturn<number>, 'sequenceId'>;
-    indexes: { sessionId: string | number };
+    indexes: { sessionId: number };
   };
 }
 
@@ -105,7 +105,7 @@ export class SessionReplayEventsIDBStore extends BaseEventsStore<number> {
   static async new(
     type: EventType,
     args: Omit<InstanceArgs, 'db'>,
-    sessionId?: string | number,
+    sessionId?: number,
   ): Promise<SessionReplayEventsIDBStore | undefined> {
     try {
       const dbSuffix = type === 'replay' ? '' : `_${type}`;
@@ -173,10 +173,7 @@ export class SessionReplayEventsIDBStore extends BaseEventsStore<number> {
         events: currentSequenceData.events,
       });
 
-      await this.db.put<'sessionCurrentSequence'>(currentSequenceKey, {
-        sessionId,
-        events: [],
-      });
+      await this.db.put<'sessionCurrentSequence'>(currentSequenceKey, { sessionId, events: [] });
 
       return {
         ...currentSequenceData,
@@ -254,7 +251,7 @@ export class SessionReplayEventsIDBStore extends BaseEventsStore<number> {
     }
   };
 
-  transitionFromKeyValStore = async (sessionId?: string | number) => {
+  transitionFromKeyValStore = async (sessionId?: number) => {
     try {
       const keyValDb = await keyValDatabaseExists();
       if (!keyValDb) {
diff --git a/packages/session-replay-browser/src/events/events-manager.ts b/packages/session-replay-browser/src/events/events-manager.ts
index 8a143db38..4e79b8ee9 100644
--- a/packages/session-replay-browser/src/events/events-manager.ts
+++ b/packages/session-replay-browser/src/events/events-manager.ts
@@ -24,7 +24,7 @@ export const createEventsManager = async <Type extends EventType>({
   type: Type;
   minInterval?: number;
   maxInterval?: number;
-  sessionId?: string | number;
+  sessionId?: number;
   payloadBatcher?: PayloadBatcher;
   storeType: StoreType;
 }): Promise<AmplitudeSessionReplayEventsManager<Type, string>> => {
@@ -65,7 +65,7 @@ export const createEventsManager = async <Type extends EventType>({
     sequenceId,
   }: {
     events: string[];
-    sessionId: string | number;
+    sessionId: number;
     deviceId: string;
     sequenceId?: number;
   }) => {
diff --git a/packages/session-replay-browser/src/events/events-memory-store.ts b/packages/session-replay-browser/src/events/events-memory-store.ts
index 5c79aae12..5f0ed015a 100644
--- a/packages/session-replay-browser/src/events/events-memory-store.ts
+++ b/packages/session-replay-browser/src/events/events-memory-store.ts
@@ -2,15 +2,15 @@ import { Events, SendingSequencesReturn } from '../typings/session-replay';
 import { BaseEventsStore } from './base-events-store';
 
 export class InMemoryEventsStore extends BaseEventsStore<number> {
-  private finalizedSequences: Record<number, { sessionId: string | number; events: string[] }> = {};
-  private sequences: Record<string | number, string[]> = {};
+  private finalizedSequences: Record<number, { sessionId: number; events: string[] }> = {};
+  private sequences: Record<number, string[]> = {};
   private sequenceId = 0;
 
-  private resetCurrentSequence(sessionId: string | number) {
+  private resetCurrentSequence(sessionId: number) {
     this.sequences[sessionId] = [];
   }
 
-  private addSequence(sessionId: string | number): SendingSequencesReturn<number> {
+  private addSequence(sessionId: number): SendingSequencesReturn<number> {
     const sequenceId = this.sequenceId++;
     const events = [...this.sequences[sessionId]];
     this.finalizedSequences[sequenceId] = { sessionId, events };
@@ -26,7 +26,7 @@ export class InMemoryEventsStore extends BaseEventsStore<number> {
     }));
   }
 
-  async storeCurrentSequence(sessionId: string | number): Promise<SendingSequencesReturn<number> | undefined> {
+  async storeCurrentSequence(sessionId: number): Promise<SendingSequencesReturn<number> | undefined> {
     if (!this.sequences[sessionId]) {
       return undefined;
     }
diff --git a/packages/session-replay-browser/src/helpers.ts b/packages/session-replay-browser/src/helpers.ts
index 001808232..7c5d9ec75 100644
--- a/packages/session-replay-browser/src/helpers.ts
+++ b/packages/session-replay-browser/src/helpers.ts
@@ -1,14 +1,12 @@
 import { getGlobalScope } from '@amplitude/analytics-client-common';
-import { ServerZone } from '@amplitude/analytics-types';
-import { getInputType } from '@amplitude/rrweb-snapshot';
+import { KB_SIZE, MASK_TEXT_CLASS, UNMASK_TEXT_CLASS } from './constants';
 import { DEFAULT_MASK_LEVEL, MaskLevel, PrivacyConfig, SessionReplayJoinedConfig } from './config/types';
+import { getInputType } from '@amplitude/rrweb-snapshot';
+import { ServerZone } from '@amplitude/analytics-types';
 import {
-  KB_SIZE,
-  MASK_TEXT_CLASS,
-  SESSION_REPLAY_EU_URL,
+  SESSION_REPLAY_EU_URL as SESSION_REPLAY_EU_SERVER_URL,
   SESSION_REPLAY_SERVER_URL,
-  SESSION_REPLAY_STAGING_URL,
-  UNMASK_TEXT_CLASS,
+  SESSION_REPLAY_STAGING_URL as SESSION_REPLAY_STAGING_SERVER_URL,
 } from './constants';
 import { StorageData } from './typings/session-replay';
 
@@ -111,7 +109,7 @@ export const generateHashCode = function (str: string) {
   return hash;
 };
 
-export const isSessionInSample = function (sessionId: string | number, sampleRate: number) {
+export const isSessionInSample = function (sessionId: number, sampleRate: number) {
   const hashNumber = generateHashCode(sessionId.toString());
   const absHash = Math.abs(hashNumber);
   const absHashMultiply = absHash * 31;
@@ -124,17 +122,17 @@ export const getCurrentUrl = () => {
   return globalScope?.location ? globalScope.location.href : '';
 };
 
-export const generateSessionReplayId = (sessionId: string | number, deviceId: string): string => {
+export const generateSessionReplayId = (sessionId: number, deviceId: string): string => {
   return `${deviceId}/${sessionId}`;
 };
 
 export const getServerUrl = (serverZone?: keyof typeof ServerZone): string => {
   if (serverZone === ServerZone.STAGING) {
-    return SESSION_REPLAY_STAGING_URL;
+    return SESSION_REPLAY_STAGING_SERVER_URL;
   }
 
   if (serverZone === ServerZone.EU) {
-    return SESSION_REPLAY_EU_URL;
+    return SESSION_REPLAY_EU_SERVER_URL;
   }
 
   return SESSION_REPLAY_SERVER_URL;
diff --git a/packages/session-replay-browser/src/hooks/click.ts b/packages/session-replay-browser/src/hooks/click.ts
index a70abd6be..821bcf059 100644
--- a/packages/session-replay-browser/src/hooks/click.ts
+++ b/packages/session-replay-browser/src/hooks/click.ts
@@ -21,7 +21,7 @@ export type ClickEvent = {
 export type ClickEventWithCount = ClickEvent & { count: number };
 
 type Options = {
-  sessionId: string | number;
+  sessionId: number;
   deviceIdFn: () => string | undefined;
   eventsManager: AmplitudeSessionReplayEventsManager<'interaction', string>;
 };
diff --git a/packages/session-replay-browser/src/identifiers.ts b/packages/session-replay-browser/src/identifiers.ts
index a71122a9c..a12a573ba 100644
--- a/packages/session-replay-browser/src/identifiers.ts
+++ b/packages/session-replay-browser/src/identifiers.ts
@@ -2,11 +2,11 @@ import { generateSessionReplayId } from './helpers';
 import { SessionIdentifiers as ISessionIdentifiers } from './typings/session-replay';
 
 export class SessionIdentifiers implements ISessionIdentifiers {
-  deviceId?: string;
-  sessionId?: string | number;
-  sessionReplayId?: string;
+  deviceId?: string | undefined;
+  sessionId?: number | undefined;
+  sessionReplayId?: string | undefined;
 
-  constructor({ sessionId, deviceId }: { sessionId?: string | number; deviceId?: string }) {
+  constructor({ sessionId, deviceId }: { sessionId?: number; deviceId?: string }) {
     this.deviceId = deviceId;
     this.sessionId = sessionId;
 
diff --git a/packages/session-replay-browser/src/session-replay.ts b/packages/session-replay-browser/src/session-replay.ts
index 97708603d..b0195fbf1 100644
--- a/packages/session-replay-browser/src/session-replay.ts
+++ b/packages/session-replay-browser/src/session-replay.ts
@@ -147,11 +147,11 @@ export class SessionReplay implements AmplitudeSessionReplay {
     this.initialize(true);
   }
 
-  setSessionId(sessionId: string | number, deviceId?: string) {
+  setSessionId(sessionId: number, deviceId?: string) {
     return returnWrapper(this.asyncSetSessionId(sessionId, deviceId));
   }
 
-  async asyncSetSessionId(sessionId: string | number, deviceId?: string) {
+  async asyncSetSessionId(sessionId: number, deviceId?: string) {
     const previousSessionId = this.identifiers && this.identifiers.sessionId;
     if (previousSessionId) {
       this.sendEvents(previousSessionId);
@@ -230,7 +230,7 @@ export class SessionReplay implements AmplitudeSessionReplay {
     });
   };
 
-  sendEvents(sessionId?: string | number) {
+  sendEvents(sessionId?: number) {
     const sessionIdToSend = sessionId || this.identifiers?.sessionId;
     const deviceId = this.getDeviceId();
     this.eventsManager &&
diff --git a/packages/session-replay-browser/src/typings/session-replay.ts b/packages/session-replay-browser/src/typings/session-replay.ts
index 81cb3c13e..c4f06a2f8 100644
--- a/packages/session-replay-browser/src/typings/session-replay.ts
+++ b/packages/session-replay-browser/src/typings/session-replay.ts
@@ -20,8 +20,8 @@ export type EventType = 'replay' | 'interaction';
 
 export interface SessionReplayDestinationSessionMetadata {
   type: EventType;
-  sessionId: string | number;
-  deviceId: string | undefined;
+  sessionId: number;
+  deviceId?: string;
   version?: SessionReplayVersion;
 }
 
@@ -41,7 +41,7 @@ export interface SessionReplayDestinationContext extends SessionReplayDestinatio
 
 export interface SendingSequencesReturn<KeyType> {
   sequenceId: KeyType;
-  sessionId: string | number;
+  sessionId: number;
   events: Events;
 }
 
@@ -53,28 +53,25 @@ export interface EventsStore<KeyType> {
   /**
    * Moves current sequence of events to long term storage and resets short term storage.
    */
-  storeCurrentSequence(sessionId: string | number): Promise<SendingSequencesReturn<KeyType> | undefined>;
+  storeCurrentSequence(sessionId: number): Promise<SendingSequencesReturn<KeyType> | undefined>;
   /**
    * Adds events to the current IDB sequence. Returns events that should be
    * sent to the track destination right away if should split events is true.
    */
-  addEventToCurrentSequence(
-    sessionId: string | number,
-    event: string,
-  ): Promise<SendingSequencesReturn<KeyType> | undefined>;
+  addEventToCurrentSequence(sessionId: number, event: string): Promise<SendingSequencesReturn<KeyType> | undefined>;
   /**
    * Returns the sequence id associated with the events batch.
    * @returns the new sequence id or undefined if it cannot be determined or on any error.
    */
-  storeSendingEvents(sessionId: string | number, events: Events): Promise<KeyType | undefined>;
+  storeSendingEvents(sessionId: number, events: Events): Promise<KeyType | undefined>;
   /**
    * Permanently removes the events batch for the session/sequence pair.
    */
-  cleanUpSessionEventsStore(sessionId: string | number, sequenceId?: KeyType): Promise<void>;
+  cleanUpSessionEventsStore(sessionId: number, sequenceId?: KeyType): Promise<void>;
 }
 export interface SessionIdentifiers {
   deviceId?: string;
-  sessionId?: string | number;
+  sessionId?: number;
   sessionReplayId?: string;
 }
 
@@ -82,8 +79,8 @@ export type SessionReplayOptions = Omit<Partial<SessionReplayLocalConfig & Sessi
 
 export interface AmplitudeSessionReplay {
   init: (apiKey: string, options: SessionReplayOptions) => AmplitudeReturn<void>;
-  setSessionId: (sessionId: string | number, deviceId?: string) => AmplitudeReturn<void>;
-  getSessionId: () => string | number | undefined;
+  setSessionId: (sessionId: number, deviceId?: string) => AmplitudeReturn<void>;
+  getSessionId: () => number | undefined;
   getSessionReplayProperties: () => { [key: string]: boolean | string | null };
   flush: (useRetry: boolean) => Promise<void>;
   shutdown: () => void;
@@ -118,14 +115,14 @@ export interface SessionReplayEventsManager<Type, Event> {
     event,
     deviceId,
   }: {
-    sessionId: string | number;
+    sessionId: number;
     event: { type: Type; data: Event };
     deviceId: string;
   }): void;
   /**
    * Move events in short term storage to long term storage and send immediately to the track destination.
    */
-  sendCurrentSequenceEvents({ sessionId, deviceId }: { sessionId: string | number; deviceId: string }): void;
+  sendCurrentSequenceEvents({ sessionId, deviceId }: { sessionId: number; deviceId: string }): void;
   /**
    * Flush the track destination queue immediately. This should invoke sends for all the events in the queue.
    */