diff --git a/client-dynamodb-v2/build.gradle.kts b/client-dynamodb-v2/build.gradle.kts
index 5c3c7f259..8a24b5527 100644
--- a/client-dynamodb-v2/build.gradle.kts
+++ b/client-dynamodb-v2/build.gradle.kts
@@ -39,6 +39,12 @@ dependencies {
   testImplementation(project(":backfila-embedded"))
   testImplementation(project(":client-testing"))
 
+  if (org.apache.tools.ant.taskdefs.condition.Os.isArch("aarch64")) {
+    // Without this, we can't compile on Apple Silicon currently. This is likely not necessary to
+    // have longterm, so we should remove it when platform fixes things across Square.
+    testImplementation("io.github.ganadist.sqlite4java:libsqlite4java-osx-aarch64:1.0.392")
+  }
+
   // ****************************************
   // For TESTING purposes only. We only want Misk for easy testing.
   // DO NOT turn these into regular dependencies.
diff --git a/client-dynamodb-v2/src/main/kotlin/app/cash/backfila/client/dynamodbv2/DynamoDbBackfill.kt b/client-dynamodb-v2/src/main/kotlin/app/cash/backfila/client/dynamodbv2/DynamoDbBackfill.kt
index 9483ae038..378aab7f7 100644
--- a/client-dynamodb-v2/src/main/kotlin/app/cash/backfila/client/dynamodbv2/DynamoDbBackfill.kt
+++ b/client-dynamodb-v2/src/main/kotlin/app/cash/backfila/client/dynamodbv2/DynamoDbBackfill.kt
@@ -87,4 +87,7 @@ abstract class DynamoDbBackfill<I : Any, P : Any> : Backfill {
 
   /** See [ScanRequest.setExpressionAttributeNames]. */
   open fun expressionAttributeNames(config: BackfillConfig<P>): Map<String, String>? = null
+
+  /** See [ScanRequest.setIndexName]. */
+  open fun indexName(config: BackfillConfig<P>): String? = null
 }
diff --git a/client-dynamodb-v2/src/main/kotlin/app/cash/backfila/client/dynamodbv2/UpdateInPlaceDynamoDbBackfill.kt b/client-dynamodb-v2/src/main/kotlin/app/cash/backfila/client/dynamodbv2/UpdateInPlaceDynamoDbBackfill.kt
index 96d2f8e29..f5416d143 100644
--- a/client-dynamodb-v2/src/main/kotlin/app/cash/backfila/client/dynamodbv2/UpdateInPlaceDynamoDbBackfill.kt
+++ b/client-dynamodb-v2/src/main/kotlin/app/cash/backfila/client/dynamodbv2/UpdateInPlaceDynamoDbBackfill.kt
@@ -31,7 +31,7 @@ abstract class UpdateInPlaceDynamoDbBackfill<I : Any, P : Any>(
             dynamoDbTable.tableName() to itemsToSave.map {
               WriteRequest.builder().putRequest(
                 PutRequest.builder().item(
-                  dynamoDbTable.tableSchema().itemToMap(it, false),
+                  dynamoDbTable.tableSchema().itemToMap(it, true),
                 ).build(),
               ).build()
             },
diff --git a/client-dynamodb-v2/src/main/kotlin/app/cash/backfila/client/dynamodbv2/internal/DynamoDbBackfillOperator.kt b/client-dynamodb-v2/src/main/kotlin/app/cash/backfila/client/dynamodbv2/internal/DynamoDbBackfillOperator.kt
index 80895b017..2886e5273 100644
--- a/client-dynamodb-v2/src/main/kotlin/app/cash/backfila/client/dynamodbv2/internal/DynamoDbBackfillOperator.kt
+++ b/client-dynamodb-v2/src/main/kotlin/app/cash/backfila/client/dynamodbv2/internal/DynamoDbBackfillOperator.kt
@@ -133,6 +133,7 @@ class DynamoDbBackfillOperator<I : Any, P : Any>(
         .filterExpression(backfill.filterExpression(config))
         .expressionAttributeValues(backfill.expressionAttributeValues(config))
         .expressionAttributeNames(backfill.expressionAttributeNames(config))
+        .indexName(backfill.indexName(config))
         .build()
 
       val result = dynamoDbClient.scan(scanRequest)
diff --git a/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/BackfillsModule.kt b/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/BackfillsModule.kt
index 2ceb57e62..bf17a3769 100644
--- a/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/BackfillsModule.kt
+++ b/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/BackfillsModule.kt
@@ -29,5 +29,6 @@ class BackfillsModule : KAbstractModule() {
     install(DynamoDbBackfillModule.create<DynamoDbLastEvaluatedKeyTest.PausingBackfill>())
     install(DynamoDbBackfillModule.create<DynamoDbBillingModeTest.EmptyTrackBackfill>())
     install(DynamoDbBackfillModule.create<DynamoDbBillingModeTest.ReallyExpensiveBackfill>())
+    install(DynamoDbBackfillModule.create<DynamoDbIndexTest.MakeTracksAsSinglesBackfill>())
   }
 }
diff --git a/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/DynamoDbIndexTest.kt b/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/DynamoDbIndexTest.kt
new file mode 100644
index 000000000..246e3a18c
--- /dev/null
+++ b/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/DynamoDbIndexTest.kt
@@ -0,0 +1,94 @@
+package app.cash.backfila.client.dynamodbv2
+
+import app.cash.backfila.client.BackfillConfig
+import app.cash.backfila.client.misk.TestingModule
+import app.cash.backfila.embedded.Backfila
+import app.cash.backfila.embedded.createWetRun
+import javax.inject.Inject
+import misk.testing.MiskTest
+import misk.testing.MiskTestModule
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import software.amazon.awssdk.enhanced.dynamodb.DynamoDbEnhancedClient
+import software.amazon.awssdk.enhanced.dynamodb.DynamoDbTable
+import software.amazon.awssdk.enhanced.dynamodb.Key
+import software.amazon.awssdk.enhanced.dynamodb.TableSchema
+import software.amazon.awssdk.enhanced.dynamodb.model.ScanEnhancedRequest
+import software.amazon.awssdk.services.dynamodb.DynamoDbClient
+
+@MiskTest(startService = true)
+class DynamoDbIndexTest {
+  @Suppress("unused")
+  @MiskTestModule
+  val module = TestingModule()
+
+  @Inject
+  lateinit var dynamoDb: DynamoDbTable<TrackItem>
+
+  @Inject
+  lateinit var backfila: Backfila
+
+  @Inject
+  lateinit var testData: TrackData
+
+  @Test
+  fun `only items in the specified index are processed`() {
+    val trackItem = TrackItem().apply {
+      this.album_token = "ALBUM_2"
+      this.sort_key = "TRACK_03"
+      this.track_title = "Thriller"
+      this.album_title = "MJ"
+    }
+    dynamoDb.putItem(trackItem)
+
+    val trackItem2 = TrackItem().apply {
+      this.album_token = "ALBUM_3"
+      this.sort_key = "TRACK_01"
+      this.track_title = "Anon"
+      // No album title so its excluded from the trackTitleIndex sparse GSI.
+    }
+    dynamoDb.putItem(trackItem2)
+
+    assertThat(rowsInIndex().size).isEqualTo(1)
+    assertThat(testData.getRowsDump().size).isEqualTo(2)
+
+    val run = backfila.createWetRun<MakeTracksAsSinglesBackfill>()
+    run.execute()
+
+    // Only rows from the index were updated.
+    assertThat(dynamoDb.getItem(Key.builder().partitionValue("ALBUM_2").sortValue("TRACK_03").build()).track_title)
+      .isEqualTo("Thriller (Single)")
+    assertThat(dynamoDb.getItem(Key.builder().partitionValue("ALBUM_3").sortValue("TRACK_01").build()).track_title)
+      .isEqualTo("Anon")
+  }
+
+  private fun rowsInIndex(): List<TrackItem> {
+    val scanRequest = ScanEnhancedRequest.builder()
+      .limit(10000)
+      .build()
+    return dynamoDb.index("trackTitleIndex").scan(scanRequest).stream().flatMap { it.items().stream() }.toList()
+  }
+
+  class MakeTracksAsSinglesBackfill @Inject constructor(
+    dynamoDb: DynamoDbClient,
+    private val dynamoDbEnhancedClient: DynamoDbEnhancedClient,
+  ) : UpdateInPlaceDynamoDbBackfill<TrackItem, MakeTracksAsSinglesBackfill.SingleParameters>(dynamoDb) {
+
+    override fun runOne(item: TrackItem, config: BackfillConfig<SingleParameters>): Boolean {
+      val trackTitle = item.track_title ?: return false
+      if (trackTitle.endsWith(" (Single)")) return true
+      item.track_title = "$trackTitle (Single)"
+      return true
+    }
+
+    data class SingleParameters(val validate: Boolean = true)
+
+    override fun indexName(config: BackfillConfig<SingleParameters>): String? = "trackTitleIndex"
+    override fun dynamoDbTable(): DynamoDbTable<TrackItem> {
+      return dynamoDbEnhancedClient.table(
+        TrackItem.TABLE_NAME,
+        TableSchema.fromClass(TrackItem::class.java),
+      )
+    }
+  }
+}
diff --git a/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/TestingModule.kt b/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/TestingModule.kt
index 97a8a6535..94cabcee5 100644
--- a/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/TestingModule.kt
+++ b/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/TestingModule.kt
@@ -13,7 +13,10 @@ import misk.inject.KAbstractModule
 import misk.logging.LogCollectorModule
 import software.amazon.awssdk.enhanced.dynamodb.DynamoDbEnhancedClient
 import software.amazon.awssdk.enhanced.dynamodb.TableSchema
+import software.amazon.awssdk.enhanced.dynamodb.model.EnhancedGlobalSecondaryIndex
 import software.amazon.awssdk.services.dynamodb.DynamoDbClient
+import software.amazon.awssdk.services.dynamodb.model.ProjectionType
+import software.amazon.awssdk.services.dynamodb.model.ProvisionedThroughput
 
 /**
  * Simulates a specific service implementation module
@@ -27,7 +30,24 @@ class TestingModule : KAbstractModule() {
 
     install(EmbeddedBackfilaModule())
 
-    install(InProcessDynamoDbModule(DynamoDbTable(TrackItem.TABLE_NAME, TrackItem::class)))
+    install(
+      InProcessDynamoDbModule(
+        DynamoDbTable(TrackItem.TABLE_NAME, TrackItem::class) { table ->
+          val provisionedThroughput = ProvisionedThroughput.builder()
+            .readCapacityUnits(100)
+            .writeCapacityUnits(100)
+            .build()
+          table.globalSecondaryIndices(
+            EnhancedGlobalSecondaryIndex.builder()
+              .indexName("trackTitleIndex")
+              .projection { it.projectionType(ProjectionType.KEYS_ONLY) }
+              .provisionedThroughput(provisionedThroughput)
+              .build(),
+          )
+          table
+        },
+      ),
+    )
   }
 
   @Provides
diff --git a/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/TrackItem.kt b/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/TrackItem.kt
index e3ee29c13..d5bf5444a 100644
--- a/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/TrackItem.kt
+++ b/client-dynamodb-v2/src/test/kotlin/app/cash/backfila/client/dynamodbv2/TrackItem.kt
@@ -2,6 +2,8 @@ package app.cash.backfila.client.dynamodbv2
 
 import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbBean
 import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbPartitionKey
+import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbSecondaryPartitionKey
+import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbSecondarySortKey
 import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbSortKey
 
 @DynamoDbBean()
@@ -17,8 +19,10 @@ class TrackItem {
   @get:DynamoDbSortKey
   var sort_key: String? = null
 
+  @get:DynamoDbSecondaryPartitionKey(indexNames = ["trackTitleIndex"])
   var track_title: String? = null
 
+  @get:DynamoDbSecondarySortKey(indexNames = ["trackTitleIndex"])
   var album_title: String? = null
 
   var artist_name: String? = null