diff --git a/packages/firestore/src/local/indexeddb_schema.ts b/packages/firestore/src/local/indexeddb_schema.ts
index 74eb68d29d8..37310a891b6 100644
--- a/packages/firestore/src/local/indexeddb_schema.ts
+++ b/packages/firestore/src/local/indexeddb_schema.ts
@@ -16,6 +16,7 @@
  */
 
 import { BatchId, ListenSequenceNumber, TargetId } from '../core/types';
+import { IndexKind } from '../model/field_index';
 import { ResourcePath } from '../model/path';
 import { BundledQuery } from '../protos/firestore_bundle_proto';
 import {
@@ -31,6 +32,11 @@ import {
   encodeResourcePath
 } from './encoded_resource_path';
 
+// TODO(indexing): Remove this constant
+const INDEXING_ENABLED = false;
+
+export const INDEXING_SCHEMA_VERSION = 12;
+
 /**
  * Schema Version for the Web client:
  * 1.  Initial version including Mutation Queue, Query Cache, and Remote
@@ -49,8 +55,9 @@ import {
  *     an auto-incrementing ID. This is required for Index-Free queries.
  * 10. Rewrite the canonical IDs to the explicit Protobuf-based format.
  * 11. Add bundles and named_queries for bundle support.
+ * 12. Add indexing support.
  */
-export const SCHEMA_VERSION = 11;
+export const SCHEMA_VERSION = INDEXING_ENABLED ? INDEXING_SCHEMA_VERSION : 11;
 
 /**
  * Wrapper class to store timestamps (seconds and nanos) in IndexedDb objects.
@@ -655,9 +662,7 @@ export type DbClientMetadataKey = string;
 
 export type DbBundlesKey = string;
 
-/**
- * A object representing a bundle loaded by the SDK.
- */
+/** An object representing a bundle loaded by the SDK. */
 export class DbBundle {
   /** Name of the IndexedDb object store. */
   static store = 'bundles';
@@ -676,9 +681,7 @@ export class DbBundle {
 
 export type DbNamedQueriesKey = string;
 
-/**
- * A object representing a named query loaded by the SDK via a bundle.
- */
+/** An object representing a named query loaded by the SDK via a bundle. */
 export class DbNamedQuery {
   /** Name of the IndexedDb object store. */
   static store = 'namedQueries';
@@ -695,6 +698,101 @@ export class DbNamedQuery {
   ) {}
 }
 
+/** The key for each index consisting of just the index id. */
+export type DbIndexConfigurationKey = number;
+
+/** An object representing the global configuration for a field index. */
+export class DbIndexConfiguration {
+  /** Name of the IndexedDb object store. */
+  static store = 'indexConfiguration';
+
+  static keyPath = 'indexId';
+
+  constructor(
+    /** The index id for this entry. */
+    public indexId: number,
+    /** The collection group this index belongs to. */
+    public collectionGroup: string,
+    /** The fields to index for this index. */
+    public fields: [[name: string, kind: IndexKind]]
+  ) {}
+}
+
+/** The key for each index state consisting of the index id and its user id. */
+export type DbIndexStateKey = [number, string];
+
+/**
+ * An object describing how up-to-date the index backfill is for each user and
+ * index.
+ */
+export class DbIndexState {
+  /** Name of the IndexedDb object store. */
+  static store = 'indexState';
+
+  static keyPath = ['indexId', 'uid'];
+
+  constructor(
+    /** The index id for this entry. */
+    public indexId: number,
+    /** The user id for this entry. */
+    public uid: string,
+    /**
+     * A number that indicates when the index was last updated (relative to
+     * other indexes).
+     */
+    public sequenceNumber: number,
+    /**
+     * The latest read time that has been indexed by Firestore for this field
+     * index. Set to `{seconds: 0, nanos: 0}` if no documents have been indexed.
+     */
+    public readTime: DbTimestamp,
+    /**
+     * The last document that has been indexed for this field index. Empty if
+     * no documents have been indexed.
+     */
+    public documentKey: EncodedResourcePath,
+    /**
+     * The largest mutation batch id that has been processed for this index. -1
+     * if no mutations have been indexed.
+     */
+    public largestBatchId: number
+  ) {}
+}
+
+/**
+ * The key for each index entry consists of the index id and its user id,
+ * the encoded array and directional value for the indexed fields as well as
+ * the encoded document path for the indexed document.
+ */
+export type DbIndexEntryKey = [number, string, Uint8Array, Uint8Array, string];
+
+/** An object that stores the encoded entries for all documents and fields. */
+export class DbIndexEntries {
+  /** Name of the IndexedDb object store. */
+  static store = 'indexEntries';
+
+  static keyPath = [
+    'indexId',
+    'uid',
+    'arrayValue',
+    'directionalValue',
+    'documentKey'
+  ];
+
+  constructor(
+    /** The index id for this entry. */
+    public indexId: number,
+    /** The user id for this entry. */
+    public uid: string,
+    /** The encoded array index value for this entry. */
+    public arrayValue: Uint8Array,
+    /** The encoded directional value for equality and inequality filters. */
+    public directionalValue: Uint8Array,
+    /** The document key this entry points to. */
+    public documentKey: EncodedResourcePath
+  ) {}
+}
+
 // Visible for testing
 export const V1_STORES = [
   DbMutationQueue.store,
@@ -712,7 +810,6 @@ export const V1_STORES = [
 // Visible for testing
 export const V3_STORES = V1_STORES;
 
-// Visible for testing
 // Note: DbRemoteDocumentChanges is no longer used and dropped with v9.
 export const V4_STORES = [...V3_STORES, DbClientMetadata.store];
 
@@ -730,6 +827,13 @@ export const V8_STORES = [...V6_STORES, DbCollectionParent.store];
 
 export const V11_STORES = [...V8_STORES, DbBundle.store, DbNamedQuery.store];
 
+export const V12_STORES = [
+  ...V11_STORES,
+  DbIndexConfiguration.store,
+  DbIndexState.store,
+  DbIndexEntries.store
+];
+
 /**
  * The list of all default IndexedDB stores used throughout the SDK. This is
  * used when creating transactions so that access across all stores is done
diff --git a/packages/firestore/src/local/indexeddb_schema_converter.ts b/packages/firestore/src/local/indexeddb_schema_converter.ts
index 1ba82e92322..f17a4c23723 100644
--- a/packages/firestore/src/local/indexeddb_schema_converter.ts
+++ b/packages/firestore/src/local/indexeddb_schema_converter.ts
@@ -35,6 +35,9 @@ import {
   DbCollectionParentKey,
   DbDocumentMutation,
   DbDocumentMutationKey,
+  DbIndexConfiguration,
+  DbIndexEntries,
+  DbIndexState,
   DbMutationBatch,
   DbMutationBatchKey,
   DbMutationQueue,
@@ -51,7 +54,7 @@ import {
   DbTargetGlobal,
   DbTargetGlobalKey,
   DbTargetKey,
-  SCHEMA_VERSION
+  INDEXING_SCHEMA_VERSION
 } from './indexeddb_schema';
 import {
   fromDbMutationBatch,
@@ -80,10 +83,10 @@ export class SchemaConverter implements SimpleDbSchemaConverter {
     fromVersion: number,
     toVersion: number
   ): PersistencePromise<void> {
-    hardAssert(
+    debugAssert(
       fromVersion < toVersion &&
         fromVersion >= 0 &&
-        toVersion <= SCHEMA_VERSION,
+        toVersion <= INDEXING_SCHEMA_VERSION,
       `Unexpected schema upgrade from v${fromVersion} to v${toVersion}.`
     );
 
@@ -169,6 +172,13 @@ export class SchemaConverter implements SimpleDbSchemaConverter {
         createNamedQueriesStore(db);
       });
     }
+
+    if (fromVersion < 12 && toVersion >= 12) {
+      p = p.next(() => {
+        createFieldIndex(db);
+      });
+    }
+
     return p;
   }
 
@@ -504,3 +514,15 @@ function createNamedQueriesStore(db: IDBDatabase): void {
     keyPath: DbNamedQuery.keyPath
   });
 }
+
+function createFieldIndex(db: IDBDatabase): void {
+  db.createObjectStore(DbIndexConfiguration.store, {
+    keyPath: DbIndexConfiguration.keyPath
+  });
+  db.createObjectStore(DbIndexState.store, {
+    keyPath: DbIndexState.keyPath
+  });
+  db.createObjectStore(DbIndexEntries.store, {
+    keyPath: DbIndexEntries.keyPath
+  });
+}
diff --git a/packages/firestore/test/unit/local/indexeddb_persistence.test.ts b/packages/firestore/test/unit/local/indexeddb_persistence.test.ts
index 4185dfcc7ae..836e1287139 100644
--- a/packages/firestore/test/unit/local/indexeddb_persistence.test.ts
+++ b/packages/firestore/test/unit/local/indexeddb_persistence.test.ts
@@ -50,6 +50,7 @@ import {
   DbTargetKey,
   DbTimestamp,
   SCHEMA_VERSION,
+  V12_STORES,
   V1_STORES,
   V3_STORES,
   V4_STORES,
@@ -1024,6 +1025,14 @@ describe('IndexedDbSchema: createOrUpgradeDb', () => {
     });
   });
 
+  it('can upgrade from version 11 to 12', async () => {
+    await withDb(11, async () => {});
+    await withDb(12, async (db, version, objectStores) => {
+      expect(version).to.have.equal(12);
+      expect(objectStores).to.have.members(V12_STORES);
+    });
+  });
+
   it('downgrading throws a custom error', async function (this: Context) {
     // Upgrade to latest version
     await withDb(SCHEMA_VERSION, async (db, version) => {