diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index fb7bc03..f3f4241 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -32,8 +32,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java: ['adoptium:17']
-        scala: ['2.12.21', '2.13.18', '3.3.7']
+        java: ['adoptium:21']
+        scala: ['3.3.7']
     steps:
       - name: Checkout current branch
         uses: actions/checkout@v6
@@ -61,7 +61,7 @@ jobs:
       - name: Setup Scala and Java
         uses: coursier/setup-action@v3
         with:
-          jvm: adoptium:17
+          jvm: adoptium:21
           apps: sbt
       - name: Cache scala dependencies
         uses: coursier/cache-action@v8
diff --git a/.scalafmt.conf b/.scalafmt.conf
index 8bfd2c7..201abc0 100644
--- a/.scalafmt.conf
+++ b/.scalafmt.conf
@@ -1,6 +1,6 @@
 version = "3.1.2"
 
-runner.dialect = scala213
+runner.dialect = scala3
 maxColumn = 120
 align.preset = most
 continuationIndent.defnSite = 2
@@ -16,9 +16,3 @@ spaces {
 optIn.annotationNewlines = true
 
 rewrite.rules = [SortImports, RedundantBraces]
-
-fileOverride {
-  "glob:**/scala-3/**" {
-    runner.dialect = scala3
-  }
-}
\ No newline at end of file
diff --git a/build.sbt b/build.sbt
index 15c95d2..a4e5dc0 100644
--- a/build.sbt
+++ b/build.sbt
@@ -1,7 +1,4 @@
-val scala212 = "2.12.21"
-val scala213 = "2.13.18"
-val scala3   = "3.3.7"
-val allScala = Seq(scala212, scala213, scala3)
+val scala3 = "3.3.7"
 
 val zioVersion            = "2.1.24"
 val zioGrpcVersion        = "0.6.3"
@@ -21,18 +18,17 @@ val scalaCompatVersion    = "2.13.0"
 
 inThisBuild(
   List(
-    scalaVersion       := scala213,
-    crossScalaVersions := allScala,
-    organization       := "com.devsisters",
-    homepage           := Some(url("https://devsisters.github.io/shardcake/")),
-    licenses           := List("Apache-2.0" -> url("http://www.apache.org/licenses/LICENSE-2.0")),
-    scmInfo            := Some(
+    scalaVersion := scala3,
+    organization := "com.devsisters",
+    homepage     := Some(url("https://devsisters.github.io/shardcake/")),
+    licenses     := List("Apache-2.0" -> url("http://www.apache.org/licenses/LICENSE-2.0")),
+    scmInfo      := Some(
       ScmInfo(
         url("https://github.com/devsisters/shardcake"),
         "scm:git:git@github.com:devsisters/shardcake.git"
       )
     ),
-    developers         := List(
+    developers   := List(
       Developer(
         "ghostdogpr",
         "Pierre Ricadat",
@@ -50,7 +46,6 @@ addCommandAlias("check", "all scalafmtSbtCheck scalafmtCheck test:scalafmtCheck"
 lazy val root = project
   .in(file("."))
   .settings(publish / skip := true)
-  .settings(crossScalaVersions := Nil)
   .aggregate(
     core,
     manager,
@@ -228,35 +223,8 @@ lazy val commonSettings = Def.settings(
     "-language:existentials",
     "-unchecked",
     "-Xfatal-warnings",
-    "-language:postfixOps"
-  ) ++ (CrossVersion.partialVersion(scalaVersion.value) match {
-    case Some((2, 12)) =>
-      Seq(
-        "-Xsource:2.13",
-        "-Yno-adapted-args",
-        "-Ypartial-unification",
-        "-Ywarn-extra-implicit",
-        "-Ywarn-inaccessible",
-        "-Ywarn-infer-any",
-        "-Ywarn-unused:-nowarn",
-        "-Ywarn-nullary-override",
-        "-Ywarn-nullary-unit",
-        "-opt-inline-from:<source>",
-        "-opt-warnings",
-        "-opt:l:inline",
-        "-explaintypes"
-      )
-    case Some((2, 13)) =>
-      Seq(
-        "-Xlint:-byname-implicit",
-        "-explaintypes"
-      )
-
-    case Some((3, _)) =>
-      Seq(
-        "-explain-types",
-        "-Ykind-projector"
-      )
-    case _            => Nil
-  })
+    "-language:postfixOps",
+    "-explain-types",
+    "-Ykind-projector"
+  )
 )
diff --git a/manager/src/main/scala/com/devsisters/shardcake/ShardManager.scala b/manager/src/main/scala/com/devsisters/shardcake/ShardManager.scala
index 0e0c68e..0a36957 100644
--- a/manager/src/main/scala/com/devsisters/shardcake/ShardManager.scala
+++ b/manager/src/main/scala/com/devsisters/shardcake/ShardManager.scala
@@ -499,15 +499,13 @@ object ShardManager {
           case Some((podAddress, shards)) =>
             val oldPodAddress = state.shards.get(shard).flatten
             // if old pod is same as new pod, don't change anything
-            if (oldPodAddress.contains(podAddress))
-              (shardsPerPod, assignments)
+            if (oldPodAddress.contains(podAddress)) (shardsPerPod, assignments)
             // if the new pod has more, as much, or only 1 less shard than the old pod, don't change anything
             else if (
               shardsPerPod.get(podAddress).fold(0)(_.size) + 1 >= oldPodAddress.fold(Int.MaxValue)(
                 shardsPerPod.getOrElse(_, Nil).size
               )
-            )
-              (shardsPerPod, assignments)
+            ) (shardsPerPod, assignments)
             // otherwise, create a new assignment
             else {
               val unassigned =