diff --git a/core/shared/src/main/scala/works/iterative/core/service/Factory.scala b/core/shared/src/main/scala/works/iterative/core/service/Factory.scala
new file mode 100644
index 0000000..c3174e4
--- /dev/null
+++ b/core/shared/src/main/scala/works/iterative/core/service/Factory.scala
@@ -0,0 +1,17 @@
+package works.iterative.core
+package service
+
+import zio.*
+
+trait EntityFactory[Entity, Seed]:
+  def make(seed: Seed): IO[UserMessage, Entity]
+
+class GeneratingFactory[Entity, Seed, Id](
+    constructor: Seed => Validated[Id => Entity],
+    idGenerator: IdGenerator[Id]
+) extends EntityFactory[Entity, Seed]:
+  override def make(seed: Seed): IO[UserMessage, Entity] =
+    for
+      construct <- constructor(seed).toZIO
+      id <- idGenerator.nextId
+    yield construct(id)

diff --git a/core/shared/src/main/scala/works/iterative/core/service/Factory.scala b/core/shared/src/main/scala/works/iterative/core/service/Factory.scala
new file mode 100644
index 0000000..c3174e4
--- /dev/null
+++ b/core/shared/src/main/scala/works/iterative/core/service/Factory.scala
@@ -0,0 +1,17 @@
+package works.iterative.core
+package service
+
+import zio.*
+
+trait EntityFactory[Entity, Seed]:
+  def make(seed: Seed): IO[UserMessage, Entity]
+
+class GeneratingFactory[Entity, Seed, Id](
+    constructor: Seed => Validated[Id => Entity],
+    idGenerator: IdGenerator[Id]
+) extends EntityFactory[Entity, Seed]:
+  override def make(seed: Seed): IO[UserMessage, Entity] =
+    for
+      construct <- constructor(seed).toZIO
+      id <- idGenerator.nextId
+    yield construct(id)
diff --git a/core/shared/src/main/scala/works/iterative/core/service/IdGenerator.scala b/core/shared/src/main/scala/works/iterative/core/service/IdGenerator.scala
new file mode 100644
index 0000000..5174e05
--- /dev/null
+++ b/core/shared/src/main/scala/works/iterative/core/service/IdGenerator.scala
@@ -0,0 +1,6 @@
+package works.iterative.core.service
+
+import zio.*
+
+trait IdGenerator[A]:
+  def nextId: UIO[A]