diff --git a/contract-tests/index.js b/contract-tests/index.js
index 3b507ffca..e3716a367 100644
--- a/contract-tests/index.js
+++ b/contract-tests/index.js
@@ -27,6 +27,8 @@ app.get('/', (req, res) => {
       'all-flags-with-reasons',
       'tags',
       'big-segments',
+      'filtering',
+      'filtering-strict',
       'user-type',
       'migrations',
       'event-sampling',
@@ -35,7 +37,7 @@ app.get('/', (req, res) => {
       'inline-context',
       'anonymous-redaction',
       'evaluation-hooks',
-      'wrapper'
+      'wrapper',
     ],
   });
 });
diff --git a/contract-tests/sdkClientEntity.js b/contract-tests/sdkClientEntity.js
index 930afdeeb..a40d7703e 100644
--- a/contract-tests/sdkClientEntity.js
+++ b/contract-tests/sdkClientEntity.js
@@ -26,11 +26,17 @@ export function makeSdkConfig(options, tag) {
   if (options.streaming) {
     cf.streamUri = options.streaming.baseUri;
     cf.streamInitialReconnectDelay = maybeTime(options.streaming.initialRetryDelayMs);
+    if (options.streaming.filter) {
+      cf.payloadFilterKey = options.streaming.filter;
+    }
   }
   if (options.polling) {
     cf.stream = false;
     cf.baseUri = options.polling.baseUri;
     cf.pollInterface = options.polling.pollIntervalMs / 1000;
+    if (options.polling.filter) {
+      cf.payloadFilterKey = options.polling.filter;
+    }
   }
   if (options.events) {
     cf.allAttributesPrivate = options.events.allAttributesPrivate;
diff --git a/packages/shared/common/__tests__/options/ServiceEndpoints.test.ts b/packages/shared/common/__tests__/options/ServiceEndpoints.test.ts
index ffa7bf5bc..c08d09f8d 100644
--- a/packages/shared/common/__tests__/options/ServiceEndpoints.test.ts
+++ b/packages/shared/common/__tests__/options/ServiceEndpoints.test.ts
@@ -1,4 +1,8 @@
-import ServiceEndpoints from '../../src/options/ServiceEndpoints';
+import ServiceEndpoints, {
+  getEventsUri,
+  getPollingUri,
+  getStreamingUri,
+} from '../../src/options/ServiceEndpoints';
 
 describe.each([
   [
@@ -33,3 +37,26 @@ describe.each([
     expect(endpoints.events).toEqual(expected.eventsUri);
   });
 });
+
+it('applies payload filter to polling and streaming endpoints', () => {
+  const endpoints = new ServiceEndpoints(
+    'https://stream.launchdarkly.com',
+    'https://sdk.launchdarkly.com',
+    'https://events.launchdarkly.com',
+    '/bulk',
+    '/diagnostic',
+    true,
+    'filterKey',
+  );
+
+  expect(getStreamingUri(endpoints, '/all', [])).toEqual(
+    'https://stream.launchdarkly.com/all?filter=filterKey',
+  );
+  expect(getPollingUri(endpoints, '/sdk/latest-all', [])).toEqual(
+    'https://sdk.launchdarkly.com/sdk/latest-all?filter=filterKey',
+  );
+  expect(
+    getPollingUri(endpoints, '/sdk/latest-all', [{ key: 'withReasons', value: 'true' }]),
+  ).toEqual('https://sdk.launchdarkly.com/sdk/latest-all?withReasons=true&filter=filterKey');
+  expect(getEventsUri(endpoints, '/bulk', [])).toEqual('https://events.launchdarkly.com/bulk');
+});
diff --git a/packages/shared/common/src/internal/events/EventSender.ts b/packages/shared/common/src/internal/events/EventSender.ts
index 30b161aba..afee52df1 100644
--- a/packages/shared/common/src/internal/events/EventSender.ts
+++ b/packages/shared/common/src/internal/events/EventSender.ts
@@ -10,7 +10,7 @@ import {
   isHttpRecoverable,
   LDUnexpectedResponseError,
 } from '../../errors';
-import { ClientContext } from '../../options';
+import { ClientContext, getEventsUri } from '../../options';
 import { defaultHeaders, httpErrorMessage, sleep } from '../../utils';
 
 export default class EventSender implements LDEventSender {
@@ -26,19 +26,18 @@ export default class EventSender implements LDEventSender {
     const { basicConfiguration, platform } = clientContext;
     const {
       sdkKey,
-      serviceEndpoints: {
-        events,
-        analyticsEventPath,
-        diagnosticEventPath,
-        includeAuthorizationHeader,
-      },
+      serviceEndpoints: { analyticsEventPath, diagnosticEventPath, includeAuthorizationHeader },
       tags,
     } = basicConfiguration;
     const { crypto, info, requests } = platform;
 
     this.defaultHeaders = defaultHeaders(sdkKey, info, tags, includeAuthorizationHeader);
-    this.eventsUri = `${events}${analyticsEventPath}`;
-    this.diagnosticEventsUri = `${events}${diagnosticEventPath}`;
+    this.eventsUri = getEventsUri(basicConfiguration.serviceEndpoints, analyticsEventPath, []);
+    this.diagnosticEventsUri = getEventsUri(
+      basicConfiguration.serviceEndpoints,
+      diagnosticEventPath,
+      [],
+    );
     this.requests = requests;
     this.crypto = crypto;
   }
diff --git a/packages/shared/common/src/internal/stream/StreamingProcessor.test.ts b/packages/shared/common/src/internal/stream/StreamingProcessor.test.ts
index 0fd17d9f4..e91b93e16 100644
--- a/packages/shared/common/src/internal/stream/StreamingProcessor.test.ts
+++ b/packages/shared/common/src/internal/stream/StreamingProcessor.test.ts
@@ -107,6 +107,7 @@ describe('given a stream processor with mock event source', () => {
         platform: basicPlatform,
       },
       '/all',
+      [],
       listeners,
       diagnosticsManager,
       mockErrorHandler,
@@ -142,6 +143,7 @@ describe('given a stream processor with mock event source', () => {
         platform: basicPlatform,
       },
       '/all',
+      [],
       listeners,
       diagnosticsManager,
       mockErrorHandler,
diff --git a/packages/shared/common/src/internal/stream/StreamingProcessor.ts b/packages/shared/common/src/internal/stream/StreamingProcessor.ts
index db67c4647..d9ccfaab4 100644
--- a/packages/shared/common/src/internal/stream/StreamingProcessor.ts
+++ b/packages/shared/common/src/internal/stream/StreamingProcessor.ts
@@ -9,6 +9,7 @@ import {
 import { LDStreamProcessor } from '../../api/subsystem';
 import { LDStreamingError } from '../../errors';
 import { ClientContext } from '../../options';
+import { getStreamingUri } from '../../options/ServiceEndpoints';
 import { defaultHeaders, httpErrorMessage, shouldRetry } from '../../utils';
 import { DiagnosticsManager } from '../diagnostics';
 import { StreamingErrorHandler } from './types';
@@ -37,6 +38,7 @@ class StreamingProcessor implements LDStreamProcessor {
     sdkKey: string,
     clientContext: ClientContext,
     streamUriPath: string,
+    parameters: { key: string; value: string }[],
     private readonly listeners: Map<EventName, ProcessStreamResponse>,
     private readonly diagnosticsManager?: DiagnosticsManager,
     private readonly errorHandler?: StreamingErrorHandler,
@@ -49,7 +51,11 @@ class StreamingProcessor implements LDStreamProcessor {
     this.headers = defaultHeaders(sdkKey, info, tags);
     this.logger = logger;
     this.requests = requests;
-    this.streamUri = `${basicConfiguration.serviceEndpoints.streaming}${streamUriPath}`;
+    this.streamUri = getStreamingUri(
+      basicConfiguration.serviceEndpoints,
+      streamUriPath,
+      parameters,
+    );
   }
 
   private logConnectionStarted() {
diff --git a/packages/shared/common/src/options/ServiceEndpoints.ts b/packages/shared/common/src/options/ServiceEndpoints.ts
index 4debefa46..d0781b0a9 100644
--- a/packages/shared/common/src/options/ServiceEndpoints.ts
+++ b/packages/shared/common/src/options/ServiceEndpoints.ts
@@ -2,6 +2,10 @@ function canonicalizeUri(uri: string): string {
   return uri.replace(/\/+$/, '');
 }
 
+function canonicalizePath(path: string): string {
+  return path.replace(/^\/+/, '').replace(/\?$/, '');
+}
+
 /**
  * Specifies the base service URIs used by SDK components.
  */
@@ -11,6 +15,7 @@ export default class ServiceEndpoints {
   public readonly streaming: string;
   public readonly polling: string;
   public readonly events: string;
+  public readonly payloadFilterKey?: string;
 
   /** Valid paths are:
    * /bulk
@@ -36,6 +41,7 @@ export default class ServiceEndpoints {
     analyticsEventPath: string = '/bulk',
     diagnosticEventPath: string = '/diagnostic',
     includeAuthorizationHeader: boolean = true,
+    payloadFilterKey?: string,
   ) {
     this.streaming = canonicalizeUri(streaming);
     this.polling = canonicalizeUri(polling);
@@ -43,5 +49,76 @@ export default class ServiceEndpoints {
     this.analyticsEventPath = analyticsEventPath;
     this.diagnosticEventPath = diagnosticEventPath;
     this.includeAuthorizationHeader = includeAuthorizationHeader;
+    this.payloadFilterKey = payloadFilterKey;
   }
 }
+
+function getWithParams(uri: string, parameters: { key: string; value: string }[]) {
+  if (parameters.length === 0) {
+    return uri;
+  }
+
+  const parts = parameters.map(({ key, value }) => `${key}=${value}`);
+  return `${uri}?${parts.join('&')}`;
+}
+
+/**
+ * Get the URI for the streaming endpoint.
+ *
+ * @param endpoints The service endpoints.
+ * @param path The path to the resource, devoid of any query parameters or hrefs.
+ * @param parameters The query parameters. These query parameters must already have the appropriate encoding applied. This function WILL NOT apply it for you.
+ */
+export function getStreamingUri(
+  endpoints: ServiceEndpoints,
+  path: string,
+  parameters: { key: string; value: string }[],
+): string {
+  const canonicalizedPath = canonicalizePath(path);
+
+  const combinedParameters = [...parameters];
+  if (endpoints.payloadFilterKey) {
+    combinedParameters.push({ key: 'filter', value: endpoints.payloadFilterKey });
+  }
+
+  return getWithParams(`${endpoints.streaming}/${canonicalizedPath}`, combinedParameters);
+}
+
+/**
+ * Get the URI for the polling endpoint.
+ *
+ * @param endpoints The service endpoints.
+ * @param path The path to the resource, devoid of any query parameters or hrefs.
+ * @param parameters The query parameters. These query parameters must already have the appropriate encoding applied. This function WILL NOT apply it for you.
+ */
+export function getPollingUri(
+  endpoints: ServiceEndpoints,
+  path: string,
+  parameters: { key: string; value: string }[],
+): string {
+  const canonicalizedPath = canonicalizePath(path);
+
+  const combinedParameters = [...parameters];
+  if (endpoints.payloadFilterKey) {
+    combinedParameters.push({ key: 'filter', value: endpoints.payloadFilterKey });
+  }
+
+  return getWithParams(`${endpoints.polling}/${canonicalizedPath}`, combinedParameters);
+}
+
+/**
+ * Get the URI for the events endpoint.
+ *
+ * @param endpoints The service endpoints.
+ * @param path The path to the resource, devoid of any query parameters or hrefs.
+ * @param parameters The query parameters. These query parameters must already have the appropriate encoding applied. This function WILL NOT apply it for you.
+ */
+export function getEventsUri(
+  endpoints: ServiceEndpoints,
+  path: string,
+  parameters: { key: string; value: string }[],
+): string {
+  const canonicalizedPath = canonicalizePath(path);
+
+  return getWithParams(`${endpoints.events}/${canonicalizedPath}`, parameters);
+}
diff --git a/packages/shared/common/src/options/index.ts b/packages/shared/common/src/options/index.ts
index 17d7859e3..04181131c 100644
--- a/packages/shared/common/src/options/index.ts
+++ b/packages/shared/common/src/options/index.ts
@@ -1,6 +1,14 @@
 import ApplicationTags from './ApplicationTags';
 import ClientContext from './ClientContext';
 import OptionMessages from './OptionMessages';
-import ServiceEndpoints from './ServiceEndpoints';
+import ServiceEndpoints, { getEventsUri, getPollingUri, getStreamingUri } from './ServiceEndpoints';
 
-export { ApplicationTags, OptionMessages, ServiceEndpoints, ClientContext };
+export {
+  ApplicationTags,
+  OptionMessages,
+  ServiceEndpoints,
+  ClientContext,
+  getStreamingUri,
+  getPollingUri,
+  getEventsUri,
+};
diff --git a/packages/shared/common/src/validators.ts b/packages/shared/common/src/validators.ts
index 5ae8f0c0c..d294643bd 100644
--- a/packages/shared/common/src/validators.ts
+++ b/packages/shared/common/src/validators.ts
@@ -118,7 +118,7 @@ export class StringMatchingRegex extends Type<string> {
   }
 
   override is(u: unknown): u is string {
-    return !!(u as string).match(this.expression);
+    return typeof u === 'string' && !!(u as string).match(this.expression);
   }
 }
 
diff --git a/packages/shared/mocks/src/platform.ts b/packages/shared/mocks/src/platform.ts
index 3fe5ecfef..ef138ebd5 100644
--- a/packages/shared/mocks/src/platform.ts
+++ b/packages/shared/mocks/src/platform.ts
@@ -1,11 +1,7 @@
-import type { Encoding, Platform, PlatformData, Requests, SdkData, Storage } from '@common';
+import type { PlatformData, SdkData } from '@common';
 
 import { setupCrypto } from './crypto';
 
-const encoding: Encoding = {
-  btoa: (s: string) => Buffer.from(s).toString('base64'),
-};
-
 const setupInfo = () => ({
   platformData: jest.fn(
     (): PlatformData => ({
diff --git a/packages/shared/mocks/src/streamingProcessor.ts b/packages/shared/mocks/src/streamingProcessor.ts
index 2de19efc8..e596b443f 100644
--- a/packages/shared/mocks/src/streamingProcessor.ts
+++ b/packages/shared/mocks/src/streamingProcessor.ts
@@ -25,6 +25,7 @@ export const setupMockStreamingProcessor = (
       sdkKey: string,
       clientContext: ClientContext,
       streamUriPath: string,
+      parameters: { key: string; value: string }[],
       listeners: Map<EventName, ProcessStreamResponse>,
       diagnosticsManager: internal.DiagnosticsManager,
       errorHandler: internal.StreamingErrorHandler,
diff --git a/packages/shared/sdk-client/src/LDClientImpl.test.ts b/packages/shared/sdk-client/src/LDClientImpl.test.ts
index 6fd145f61..34008c497 100644
--- a/packages/shared/sdk-client/src/LDClientImpl.test.ts
+++ b/packages/shared/sdk-client/src/LDClientImpl.test.ts
@@ -112,6 +112,7 @@ describe('sdk-client object', () => {
       expect.anything(),
       '/stream/path',
       expect.anything(),
+      expect.anything(),
       undefined,
       expect.anything(),
     );
@@ -130,7 +131,8 @@ describe('sdk-client object', () => {
     expect(MockStreamingProcessor).toHaveBeenCalledWith(
       expect.anything(),
       expect.anything(),
-      '/stream/path?withReasons=true',
+      '/stream/path',
+      [{ key: 'withReasons', value: 'true' }],
       expect.anything(),
       undefined,
       expect.anything(),
diff --git a/packages/shared/sdk-client/src/LDClientImpl.ts b/packages/shared/sdk-client/src/LDClientImpl.ts
index cc8b33ad2..beac5c1c0 100644
--- a/packages/shared/sdk-client/src/LDClientImpl.ts
+++ b/packages/shared/sdk-client/src/LDClientImpl.ts
@@ -401,15 +401,17 @@ export default class LDClientImpl implements LDClient {
     identifyResolve: any,
     identifyReject: any,
   ) {
-    let pollingPath = this.createPollUriPath(context);
+    const parameters: { key: string; value: string }[] = [];
     if (this.config.withReasons) {
-      pollingPath = `${pollingPath}?withReasons=true`;
+      parameters.push({ key: 'withReasons', value: 'true' });
     }
+
     this.updateProcessor = new PollingProcessor(
       this.sdkKey,
       this.clientContext.platform.requests,
       this.clientContext.platform.info,
-      pollingPath,
+      this.createPollUriPath(context),
+      parameters,
       this.config,
       async (flags) => {
         this.logger.debug(`Handling polling result: ${Object.keys(flags)}`);
@@ -438,15 +440,16 @@ export default class LDClientImpl implements LDClient {
     identifyResolve: any,
     identifyReject: any,
   ) {
-    let streamingPath = this.createStreamUriPath(context);
+    const parameters: { key: string; value: string }[] = [];
     if (this.config.withReasons) {
-      streamingPath = `${streamingPath}?withReasons=true`;
+      parameters.push({ key: 'withReasons', value: 'true' });
     }
 
     this.updateProcessor = new internal.StreamingProcessor(
       this.sdkKey,
       this.clientContext,
-      streamingPath,
+      this.createStreamUriPath(context),
+      parameters,
       this.createStreamListeners(checkedContext, identifyResolve),
       this.diagnosticsManager,
       (e) => {
diff --git a/packages/shared/sdk-client/src/api/LDOptions.ts b/packages/shared/sdk-client/src/api/LDOptions.ts
index 97de4f8b1..8d098c881 100644
--- a/packages/shared/sdk-client/src/api/LDOptions.ts
+++ b/packages/shared/sdk-client/src/api/LDOptions.ts
@@ -224,4 +224,20 @@ export interface LDOptions {
    * If `wrapperName` is unset, this field will be ignored.
    */
   wrapperVersion?: string;
+
+  /**
+   * LaunchDarkly Server SDKs historically downloaded all flag configuration and segments for a particular environment
+   * during initialization.
+   *
+   * For some customers, this is an unacceptably large amount of data, and has contributed to performance issues
+   * within their products.
+   *
+   * Filtered environments aim to solve this problem. By allowing customers to specify subsets of an environment's
+   * flags using a filter key, SDKs will initialize faster and use less memory.
+   *
+   * This payload filter key only applies to the default streaming and polling data sources. It will not affect
+   * TestData or FileData data sources, nor will it be applied to any data source provided through the featureStore
+   * config property.
+   */
+  payloadFilterKey?: string;
 }
diff --git a/packages/shared/sdk-client/src/configuration/Configuration.test.ts b/packages/shared/sdk-client/src/configuration/Configuration.test.ts
index e5b18e59c..9936234f9 100644
--- a/packages/shared/sdk-client/src/configuration/Configuration.test.ts
+++ b/packages/shared/sdk-client/src/configuration/Configuration.test.ts
@@ -7,7 +7,7 @@ describe('Configuration', () => {
     console.error = jest.fn();
   });
 
-  test('defaults', () => {
+  it('has valid default values', () => {
     const config = new Configuration();
 
     expect(config).toMatchObject({
@@ -36,12 +36,12 @@ describe('Configuration', () => {
     expect(console.error).not.toHaveBeenCalled();
   });
 
-  test('specified options should be set', () => {
+  it('allows specifying valid wrapperName', () => {
     const config = new Configuration({ wrapperName: 'test' });
     expect(config).toMatchObject({ wrapperName: 'test' });
   });
 
-  test('unknown option', () => {
+  it('warns and ignored invalid keys', () => {
     // @ts-ignore
     const config = new Configuration({ baseballUri: 1 });
 
@@ -49,7 +49,7 @@ describe('Configuration', () => {
     expect(console.error).toHaveBeenCalledWith(expect.stringContaining('unknown config option'));
   });
 
-  test('wrong type for boolean should be converted', () => {
+  it('converts boolean types', () => {
     // @ts-ignore
     const config = new Configuration({ sendEvents: 0 });
 
@@ -59,7 +59,7 @@ describe('Configuration', () => {
     );
   });
 
-  test('wrong type for number should use default', () => {
+  it('ignores wrong type for number and logs appropriately', () => {
     // @ts-ignore
     const config = new Configuration({ capacity: true });
 
@@ -69,7 +69,7 @@ describe('Configuration', () => {
     );
   });
 
-  test('enforce minimum flushInterval', () => {
+  it('enforces minimum flushInterval', () => {
     const config = new Configuration({ flushInterval: 1 });
 
     expect(config.flushInterval).toEqual(2);
@@ -79,14 +79,14 @@ describe('Configuration', () => {
     );
   });
 
-  test('recognize maxCachedContexts', () => {
+  it('allows setting a valid maxCachedContexts', () => {
     const config = new Configuration({ maxCachedContexts: 3 });
 
     expect(config.maxCachedContexts).toBeDefined();
     expect(console.error).not.toHaveBeenCalled();
   });
 
-  test('enforce minimum maxCachedContext', () => {
+  it('enforces minimum maxCachedContext', () => {
     const config = new Configuration({ maxCachedContexts: -1 });
 
     expect(config.maxCachedContexts).toBeDefined();
@@ -95,4 +95,28 @@ describe('Configuration', () => {
       expect.stringContaining('had invalid value of -1'),
     );
   });
+
+  it.each([
+    ['1'],
+    ['camelCaseWorks'],
+    ['PascalCaseWorks'],
+    ['kebab-case-works'],
+    ['snake_case_works'],
+  ])('allow setting valid payload filter keys', (filter) => {
+    const config = new Configuration({ payloadFilterKey: filter });
+    expect(config.payloadFilterKey).toEqual(filter);
+    expect(console.error).toHaveBeenCalledTimes(0);
+  });
+
+  it.each([['invalid-@-filter'], ['_invalid-filter'], ['-invalid-filter']])(
+    'ignores invalid filters and logs a warning',
+    (filter) => {
+      const config = new Configuration({ payloadFilterKey: filter });
+      expect(config.payloadFilterKey).toBeUndefined();
+      expect(console.error).toHaveBeenNthCalledWith(
+        1,
+        expect.stringMatching(/should be of type string matching/i),
+      );
+    },
+  );
 });
diff --git a/packages/shared/sdk-client/src/configuration/Configuration.ts b/packages/shared/sdk-client/src/configuration/Configuration.ts
index 8d4507dcc..55d87f879 100644
--- a/packages/shared/sdk-client/src/configuration/Configuration.ts
+++ b/packages/shared/sdk-client/src/configuration/Configuration.ts
@@ -78,6 +78,7 @@ export default class Configuration {
       internalOptions.analyticsEventPath,
       internalOptions.diagnosticEventPath,
       internalOptions.includeAuthorizationHeader,
+      pristineOptions.payloadFilterKey,
     );
     this.tags = new ApplicationTags({ application: this.applicationInfo, logger: this.logger });
   }
diff --git a/packages/shared/sdk-client/src/configuration/validators.ts b/packages/shared/sdk-client/src/configuration/validators.ts
index 7b3aaddc9..cc22874b4 100644
--- a/packages/shared/sdk-client/src/configuration/validators.ts
+++ b/packages/shared/sdk-client/src/configuration/validators.ts
@@ -40,6 +40,7 @@ const validators: Record<keyof LDOptions, TypeValidator> = {
   applicationInfo: TypeValidators.Object,
   wrapperName: TypeValidators.String,
   wrapperVersion: TypeValidators.String,
+  payloadFilterKey: TypeValidators.stringMatchingRegex(/^[a-zA-Z0-9](\w|\.|-)*$/),
 };
 
 export default validators;
diff --git a/packages/shared/sdk-client/src/polling/PollingProcessor.ts b/packages/shared/sdk-client/src/polling/PollingProcessor.ts
index 23fe35770..2b95f27fd 100644
--- a/packages/shared/sdk-client/src/polling/PollingProcessor.ts
+++ b/packages/shared/sdk-client/src/polling/PollingProcessor.ts
@@ -1,5 +1,6 @@
 import {
   ApplicationTags,
+  getPollingUri,
   httpErrorMessage,
   HttpErrorResponse,
   Info,
@@ -48,11 +49,12 @@ export default class PollingProcessor implements subsystem.LDStreamProcessor {
     requests: Requests,
     info: Info,
     uriPath: string,
+    parameters: { key: string; value: string }[],
     config: PollingConfig,
     private readonly dataHandler: (flags: Flags) => void,
     private readonly errorHandler?: PollingErrorHandler,
   ) {
-    const uri = `${config.serviceEndpoints.polling}${uriPath}`;
+    const uri = getPollingUri(config.serviceEndpoints, uriPath, parameters);
     this.logger = config.logger;
     this.pollInterval = config.pollInterval;
 
diff --git a/packages/shared/sdk-client/src/polling/PollingProcessot.test.ts b/packages/shared/sdk-client/src/polling/PollingProcessot.test.ts
index 6114f42a5..ce0a6a8e0 100644
--- a/packages/shared/sdk-client/src/polling/PollingProcessot.test.ts
+++ b/packages/shared/sdk-client/src/polling/PollingProcessot.test.ts
@@ -86,6 +86,7 @@ it('makes no requests until it is started', () => {
     requests,
     makeInfo(),
     '/polling',
+    [],
     makeConfig(),
     (_flags) => {},
     (_error) => {},
@@ -102,6 +103,7 @@ it('polls immediately when started', () => {
     requests,
     makeInfo(),
     '/polling',
+    [],
     makeConfig(),
     (_flags) => {},
     (_error) => {},
@@ -122,6 +124,7 @@ it('calls callback on success', async () => {
     requests,
     makeInfo(),
     '/polling',
+    [],
     makeConfig(),
     dataCallback,
     errorCallback,
@@ -143,6 +146,7 @@ it('polls repeatedly', async () => {
     requests,
     makeInfo(),
     '/polling',
+    [],
     makeConfig({ pollInterval: 0.1 }),
     dataCallback,
     errorCallback,
@@ -174,6 +178,7 @@ it('stops polling when stopped', (done) => {
     requests,
     makeInfo(),
     '/stops',
+    [],
     makeConfig({ pollInterval: 0.01 }),
     dataCallback,
     errorCallback,
@@ -199,6 +204,7 @@ it('includes the correct headers on requests', () => {
       version: '42',
     }),
     '/polling',
+    [],
     makeConfig(),
     (_flags) => {},
     (_error) => {},
@@ -225,6 +231,7 @@ it('defaults to using the "GET" verb', () => {
     requests,
     makeInfo(),
     '/polling',
+    [],
     makeConfig(),
     (_flags) => {},
     (_error) => {},
@@ -248,6 +255,7 @@ it('can be configured to use the "REPORT" verb', () => {
     requests,
     makeInfo(),
     '/polling',
+    [],
     makeConfig({ useReport: true }),
     (_flags) => {},
     (_error) => {},
@@ -274,6 +282,7 @@ it('continues polling after receiving bad JSON', async () => {
     requests,
     makeInfo(),
     '/polling',
+    [],
     config,
     dataCallback,
     errorCallback,
@@ -302,6 +311,7 @@ it('continues polling after an exception thrown during a request', async () => {
     requests,
     makeInfo(),
     '/polling',
+    [],
     config,
     dataCallback,
     errorCallback,
@@ -333,6 +343,7 @@ it('can handle recoverable http errors', async () => {
     requests,
     makeInfo(),
     '/polling',
+    [],
     config,
     dataCallback,
     errorCallback,
@@ -362,6 +373,7 @@ it('stops polling on unrecoverable error codes', (done) => {
     requests,
     makeInfo(),
     '/polling',
+    [],
     config,
     dataCallback,
     errorCallback,
diff --git a/packages/shared/sdk-server/__tests__/options/Configuration.test.ts b/packages/shared/sdk-server/__tests__/options/Configuration.test.ts
index 03b6fa27d..399439be7 100644
--- a/packages/shared/sdk-server/__tests__/options/Configuration.test.ts
+++ b/packages/shared/sdk-server/__tests__/options/Configuration.test.ts
@@ -41,6 +41,7 @@ describe.each([undefined, null, 'potat0', 17, [], {}])('constructed without opti
     expect(config.wrapperName).toBeUndefined();
     expect(config.wrapperVersion).toBeUndefined();
     expect(config.hooks).toBeUndefined();
+    expect(config.payloadFilterKey).toBeUndefined();
   });
 });
 
@@ -329,6 +330,34 @@ describe('when setting different options', () => {
     logger(config).expectMessages(logs);
   });
 
+  it.each([
+    ['1', '1', []],
+    ['camelCaseWorks', 'camelCaseWorks', []],
+    ['PascalCaseWorks', 'PascalCaseWorks', []],
+    ['kebab-case-works', 'kebab-case-works', []],
+    ['snake_case_works', 'snake_case_works', []],
+    [
+      'invalid-@-filter',
+      undefined,
+      [{ level: LogLevel.Warn, matches: /Config option "payloadFilterKey" should be of type/ }],
+    ],
+    [
+      '_invalid-filter',
+      undefined,
+      [{ level: LogLevel.Warn, matches: /Config option "payloadFilterKey" should be of type/ }],
+    ],
+    [
+      '-invalid-filter',
+      undefined,
+      [{ level: LogLevel.Warn, matches: /Config option "payloadFilterKey" should be of type/ }],
+    ],
+  ])('allow setting and validates payloadFilterKey', (filter, expected, logs) => {
+    // @ts-ignore
+    const config = new Configuration(withLogger({ payloadFilterKey: filter }));
+    expect(config.payloadFilterKey).toEqual(expected);
+    logger(config).expectMessages(logs);
+  });
+
   it('discards unrecognized options with a warning', () => {
     // @ts-ignore
     const config = new Configuration(withLogger({ yes: 'no', cat: 'yes' }));
diff --git a/packages/shared/sdk-server/src/LDClientImpl.ts b/packages/shared/sdk-server/src/LDClientImpl.ts
index de271ea36..688a36b40 100644
--- a/packages/shared/sdk-server/src/LDClientImpl.ts
+++ b/packages/shared/sdk-server/src/LDClientImpl.ts
@@ -217,6 +217,7 @@ export default class LDClientImpl implements LDClient {
             sdkKey,
             clientContext,
             '/all',
+            [],
             listeners,
             this.diagnosticsManager,
             (e) => this.dataSourceErrorHandler(e),
diff --git a/packages/shared/sdk-server/src/api/options/LDOptions.ts b/packages/shared/sdk-server/src/api/options/LDOptions.ts
index a0d38b0fa..769783973 100644
--- a/packages/shared/sdk-server/src/api/options/LDOptions.ts
+++ b/packages/shared/sdk-server/src/api/options/LDOptions.ts
@@ -268,6 +268,22 @@ export interface LDOptions {
      * ASCII digits, period, hyphen, underscore. A string containing any other characters will be ignored.
      */
     versionName?: string;
+
+    /**
+     * LaunchDarkly Server SDKs historically downloaded all flag configuration and segments for a particular environment
+     * during initialization.
+     *
+     * For some customers, this is an unacceptably large amount of data, and has contributed to performance issues
+     * within their products.
+     *
+     * Filtered environments aim to solve this problem. By allowing customers to specify subsets of an environment's
+     * flags using a filter key, SDKs will initialize faster and use less memory.
+     *
+     * This payload filter key only applies to the default streaming and polling data sources. It will not affect
+     * TestData or FileData data sources, nor will it be applied to any data source provided through the featureStore
+     * config property.
+     */
+    payloadFilterKey?: string;
   };
 
   /**
diff --git a/packages/shared/sdk-server/src/data_sources/Requestor.ts b/packages/shared/sdk-server/src/data_sources/Requestor.ts
index 6ffb2200d..d6498c604 100644
--- a/packages/shared/sdk-server/src/data_sources/Requestor.ts
+++ b/packages/shared/sdk-server/src/data_sources/Requestor.ts
@@ -1,5 +1,6 @@
 import {
   defaultHeaders,
+  getPollingUri,
   Info,
   LDStreamingError,
   Options,
@@ -33,7 +34,7 @@ export default class Requestor implements LDFeatureRequestor {
     private readonly requests: Requests,
   ) {
     this.headers = defaultHeaders(sdkKey, info, config.tags);
-    this.uri = `${config.serviceEndpoints.polling}/sdk/latest-all`;
+    this.uri = getPollingUri(config.serviceEndpoints, '/sdk/latest-all', []);
   }
 
   /**
diff --git a/packages/shared/sdk-server/src/options/Configuration.ts b/packages/shared/sdk-server/src/options/Configuration.ts
index 9e68a4f20..77baf0de3 100644
--- a/packages/shared/sdk-server/src/options/Configuration.ts
+++ b/packages/shared/sdk-server/src/options/Configuration.ts
@@ -55,6 +55,7 @@ const validations: Record<string, TypeValidator> = {
   wrapperName: TypeValidators.String,
   wrapperVersion: TypeValidators.String,
   application: TypeValidators.Object,
+  payloadFilterKey: TypeValidators.stringMatchingRegex(/^[a-zA-Z0-9](\w|\.|-)*$/),
   hooks: TypeValidators.createTypeArray('Hook[]', {}),
 };
 
@@ -197,6 +198,8 @@ export default class Configuration {
 
   public readonly tags: ApplicationTags;
 
+  public readonly payloadFilterKey?: string;
+
   public readonly diagnosticRecordingInterval: number;
 
   public readonly featureStoreFactory: (clientContext: LDClientContext) => LDFeatureStore;
@@ -234,6 +237,7 @@ export default class Configuration {
       internalOptions.analyticsEventPath,
       internalOptions.diagnosticEventPath,
       internalOptions.includeAuthorizationHeader,
+      validatedOptions.payloadFilterKey,
     );
     this.eventsCapacity = validatedOptions.capacity;
     this.timeout = validatedOptions.timeout;
@@ -255,6 +259,7 @@ export default class Configuration {
     this.tlsParams = validatedOptions.tlsParams;
     this.diagnosticOptOut = validatedOptions.diagnosticOptOut;
     this.wrapperName = validatedOptions.wrapperName;
+    this.payloadFilterKey = validatedOptions.payloadFilterKey;
     this.wrapperVersion = validatedOptions.wrapperVersion;
     this.tags = new ApplicationTags(validatedOptions);
     this.diagnosticRecordingInterval = validatedOptions.diagnosticRecordingInterval;