diff --git a/packages/firestore/src/core/component_provider.ts b/packages/firestore/src/core/component_provider.ts
index 2c34723ecef..285b9e66ac0 100644
--- a/packages/firestore/src/core/component_provider.ts
+++ b/packages/firestore/src/core/component_provider.ts
@@ -162,6 +162,7 @@ export class MemoryComponentProvider implements ComponentProvider {
     return new SyncEngine(
       this.localStore,
       this.remoteStore,
+      cfg.datastore,
       this.sharedClientState,
       cfg.initialUser,
       cfg.maxConcurrentLimboResolutions
@@ -219,6 +220,7 @@ export class IndexedDbComponentProvider extends MemoryComponentProvider {
     const syncEngine = new MultiTabSyncEngine(
       this.localStore,
       this.remoteStore,
+      cfg.datastore,
       this.sharedClientState,
       cfg.initialUser,
       cfg.maxConcurrentLimboResolutions
diff --git a/packages/firestore/src/core/sync_engine.ts b/packages/firestore/src/core/sync_engine.ts
index 0204f403e50..0286c2c079f 100644
--- a/packages/firestore/src/core/sync_engine.ts
+++ b/packages/firestore/src/core/sync_engine.ts
@@ -74,6 +74,7 @@ import {
 import { ViewSnapshot } from './view_snapshot';
 import { AsyncQueue, wrapInUserErrorIfRecoverable } from '../util/async_queue';
 import { TransactionRunner } from './transaction_runner';
+import { Datastore } from '../remote/datastore';
 
 const LOG_TAG = 'SyncEngine';
 
@@ -185,6 +186,7 @@ export class SyncEngine implements RemoteSyncer {
   constructor(
     protected localStore: LocalStore,
     protected remoteStore: RemoteStore,
+    protected datastore: Datastore,
     // PORTING NOTE: Manages state synchronization in multi-tab environments.
     protected sharedClientState: SharedClientState,
     private currentUser: User,
@@ -390,7 +392,7 @@ export class SyncEngine implements RemoteSyncer {
   ): void {
     new TransactionRunner<T>(
       asyncQueue,
-      this.remoteStore,
+      this.datastore,
       updateFunction,
       deferred
     ).run();
@@ -924,6 +926,7 @@ export class MultiTabSyncEngine extends SyncEngine
   constructor(
     protected localStore: MultiTabLocalStore,
     remoteStore: RemoteStore,
+    datastore: Datastore,
     sharedClientState: SharedClientState,
     currentUser: User,
     maxConcurrentLimboResolutions: number
@@ -931,6 +934,7 @@ export class MultiTabSyncEngine extends SyncEngine
     super(
       localStore,
       remoteStore,
+      datastore,
       sharedClientState,
       currentUser,
       maxConcurrentLimboResolutions
diff --git a/packages/firestore/src/core/transaction.ts b/packages/firestore/src/core/transaction.ts
index 39f380c7950..0beefda0bf5 100644
--- a/packages/firestore/src/core/transaction.ts
+++ b/packages/firestore/src/core/transaction.ts
@@ -16,7 +16,6 @@
  */
 
 import { ParsedSetData, ParsedUpdateData } from '../api/user_data_reader';
-import { documentVersionMap } from '../model/collections';
 import { Document, MaybeDocument, NoDocument } from '../model/document';
 
 import { DocumentKey } from '../model/document_key';
@@ -34,6 +33,7 @@ import {
 import { fail, debugAssert } from '../util/assert';
 import { Code, FirestoreError } from '../util/error';
 import { SnapshotVersion } from './snapshot_version';
+import { ResourcePath } from '../model/path';
 
 /**
  * Internal transaction object responsible for accumulating the mutations to
@@ -41,7 +41,7 @@ import { SnapshotVersion } from './snapshot_version';
  */
 export class Transaction {
   // The version of each document that was read during this transaction.
-  private readVersions = documentVersionMap();
+  private readVersions = new Map</* path */ string, SnapshotVersion>();
   private mutations: Mutation[] = [];
   private committed = false;
 
@@ -106,14 +106,15 @@ export class Transaction {
     if (this.lastWriteError) {
       throw this.lastWriteError;
     }
-    let unwritten = this.readVersions;
+    const unwritten = this.readVersions;
     // For each mutation, note that the doc was written.
     this.mutations.forEach(mutation => {
-      unwritten = unwritten.remove(mutation.key);
+      unwritten.delete(mutation.key.toString());
     });
     // For each document that was read but not written to, we want to perform
     // a `verify` operation.
-    unwritten.forEach((key, _version) => {
+    unwritten.forEach((_, path) => {
+      const key = new DocumentKey(ResourcePath.fromString(path));
       this.mutations.push(new VerifyMutation(key, this.precondition(key)));
     });
     await invokeCommitRpc(this.datastore, this.mutations);
@@ -132,8 +133,8 @@ export class Transaction {
       throw fail('Document in a transaction was a ' + doc.constructor.name);
     }
 
-    const existingVersion = this.readVersions.get(doc.key);
-    if (existingVersion !== null) {
+    const existingVersion = this.readVersions.get(doc.key.toString());
+    if (existingVersion) {
       if (!docVersion.isEqual(existingVersion)) {
         // This transaction will fail no matter what.
         throw new FirestoreError(
@@ -142,7 +143,7 @@ export class Transaction {
         );
       }
     } else {
-      this.readVersions = this.readVersions.insert(doc.key, docVersion);
+      this.readVersions.set(doc.key.toString(), docVersion);
     }
   }
 
@@ -151,7 +152,7 @@ export class Transaction {
    * as a precondition, or no precondition if it was not read.
    */
   private precondition(key: DocumentKey): Precondition {
-    const version = this.readVersions.get(key);
+    const version = this.readVersions.get(key.toString());
     if (!this.writtenDocs.has(key) && version) {
       return Precondition.updateTime(version);
     } else {
@@ -163,7 +164,7 @@ export class Transaction {
    * Returns the precondition for a document if the operation is an update.
    */
   private preconditionForUpdate(key: DocumentKey): Precondition {
-    const version = this.readVersions.get(key);
+    const version = this.readVersions.get(key.toString());
     // The first time a document is written, we want to take into account the
     // read time and existence
     if (!this.writtenDocs.has(key) && version) {
diff --git a/packages/firestore/src/core/transaction_runner.ts b/packages/firestore/src/core/transaction_runner.ts
index 1c0a16acdd0..9a5879af168 100644
--- a/packages/firestore/src/core/transaction_runner.ts
+++ b/packages/firestore/src/core/transaction_runner.ts
@@ -19,7 +19,7 @@ import { Deferred } from '../util/promise';
 import { TimerId, AsyncQueue } from '../util/async_queue';
 import { ExponentialBackoff } from '../remote/backoff';
 import { Transaction } from './transaction';
-import { RemoteStore } from '../remote/remote_store';
+import { Datastore } from '../remote/datastore';
 import { isNullOrUndefined } from '../util/types';
 import { isPermanentError } from '../remote/rpc_error';
 import { FirestoreError } from '../util/error';
@@ -36,7 +36,7 @@ export class TransactionRunner<T> {
 
   constructor(
     private readonly asyncQueue: AsyncQueue,
-    private readonly remoteStore: RemoteStore,
+    private readonly datastore: Datastore,
     private readonly updateFunction: (transaction: Transaction) => Promise<T>,
     private readonly deferred: Deferred<T>
   ) {
@@ -53,7 +53,7 @@ export class TransactionRunner<T> {
 
   private runWithBackOff(): void {
     this.backoff.backoffAndRun(async () => {
-      const transaction = this.remoteStore.createTransaction();
+      const transaction = new Transaction(this.datastore);
       const userPromise = this.tryRunUpdateFunction(transaction);
       if (userPromise) {
         userPromise