diff --git a/core/src/main/scala/latis/catalog/Catalog.scala b/core/src/main/scala/latis/catalog/Catalog.scala
index 0b93f4f7..726405eb 100644
--- a/core/src/main/scala/latis/catalog/Catalog.scala
+++ b/core/src/main/scala/latis/catalog/Catalog.scala
@@ -34,14 +34,14 @@ trait Catalog { self =>
   def datasets: Stream[IO, Dataset]
 
   /** This catalog's subcatalogs. */
-  def catalogs: Map[Identifier, Catalog] = Map.empty
+  def catalogs: IO[Map[Identifier, Catalog]] = IO.pure(Map.empty)
 
   /** Adds a single subcatalog to this catalog. */
   def addCatalog(id: Identifier, catalog: Catalog): Catalog = new Catalog {
     override val datasets: Stream[IO, Dataset] = self.datasets
 
-    override val catalogs: Map[Identifier, Catalog] =
-      self.catalogs + (id -> catalog)
+    override val catalogs: IO[Map[Identifier, Catalog]] =
+      self.catalogs.map(_ + (id -> catalog))
   }
 
   /**
@@ -51,17 +51,20 @@ trait Catalog { self =>
   def filter(p: Dataset => Boolean): Catalog = new Catalog {
     override val datasets: Stream[IO, Dataset] = self.datasets.filter(p)
 
-    override val catalogs: Map[Identifier, Catalog] = self.catalogs.map {
-      case (id, cat) => id -> cat.filter(p)
+    override val catalogs: IO[Map[Identifier, Catalog]] = self.catalogs.map {
+      _.map {
+        case (id, cat) => id -> cat.filter(p)
+      }
     }
   }
 
   /** Returns a subcatalog given its name. */
-  def findCatalog(name: Identifier): Option[Catalog] =
+  def findCatalog(name: Identifier): IO[Option[Catalog]] =
     splitId(name) match {
-      case (Nil, id)     => catalogs.get(id)
+      case (Nil, id)     => catalogs.map(_.get(id))
       case (q :: qs, id) =>
-        catalogs.get(q).flatMap(_.findCatalog(concatId(qs, id)))
+        OptionT(catalogs.map(_.get(q)))
+          .flatMapF(_.findCatalog(concatId(qs, id))).value
     }
 
   /**
@@ -72,14 +75,15 @@ trait Catalog { self =>
       case (Nil, id)     =>
         datasets.find(_.id.forall(_ == id)).compile.last
       case (q :: qs, id) =>
-        catalogs.get(q).flatTraverse(_.findDataset(concatId(qs, id)))
+        OptionT(catalogs.map(_.get(q)))
+          .flatMapF(_.findDataset(concatId(qs, id))).value
     }
 
   /** Sets this catalog's subcatalogs. */
   def withCatalogs(scs: (Identifier, Catalog)*): Catalog = new Catalog {
     override val datasets: Stream[IO,Dataset] = self.datasets
 
-    override val catalogs: Map[Identifier, Catalog] = scs.toMap
+    override val catalogs: IO[Map[Identifier, Catalog]] = scs.toMap.pure[IO]
   }
 
   // Constructs a qualified ID.
diff --git a/core/src/test/scala/latis/catalog/CatalogSuite.scala b/core/src/test/scala/latis/catalog/CatalogSuite.scala
index 33f36ea0..84ef01e8 100644
--- a/core/src/test/scala/latis/catalog/CatalogSuite.scala
+++ b/core/src/test/scala/latis/catalog/CatalogSuite.scala
@@ -33,7 +33,9 @@ class CatalogSuite extends CatsEffectSuite {
   // that datasets in this list are unique.
   private def listAll(c: Catalog): IO[List[Dataset]] = {
     def go(c: Catalog): Stream[IO, Dataset] = {
-      c.datasets ++ c.catalogs.toList.foldMap { case (_, c) => go(c) }
+      c.datasets ++ Stream.eval(c.catalogs).flatMap(
+        sub => Stream.emits(sub.toList)
+      ).flatMap { case (_, c) => go(c) }
     }
     go(c).compile.toList
   }
@@ -75,8 +77,9 @@ class CatalogSuite extends CatsEffectSuite {
   }
 
   test("find catalog in a nested catalog") {
-    nested.findCatalog(id"b.c")
-      .fold(fail("Failed to find catalog"))(assertEquals(_, c2))
+    nested.findCatalog(id"b.c").map(
+      _.fold(fail("Failed to find catalog"))(assertEquals(_, c2))
+    )
   }
 
   test("find dataset in a nested catalog") {
diff --git a/dap2-service/src/main/scala/latis/service/dap2/Dap2Service.scala b/dap2-service/src/main/scala/latis/service/dap2/Dap2Service.scala
index 9f832ec9..64f8ba0c 100644
--- a/dap2-service/src/main/scala/latis/service/dap2/Dap2Service.scala
+++ b/dap2-service/src/main/scala/latis/service/dap2/Dap2Service.scala
@@ -51,7 +51,7 @@ class Dap2Service(catalog: Catalog, operationRegistry: OperationRegistry)
           // Dataset path should not end with slash
           if (path.endsWithSlash) NotFound(s"Resource not found: $path")
           else datasetResponse(ds, ext, query)
-        case None     => catalog.findCatalog(id) match {
+        case None     => catalog.findCatalog(id).flatMap {
           case Some(cat) => catalogResponse(cat, headers)
           case None      => NotFound(s"Resource not found: $path")
         }
diff --git a/dap2-service/src/main/scala/latis/service/dap2/HtmlCatalogEncoder.scala b/dap2-service/src/main/scala/latis/service/dap2/HtmlCatalogEncoder.scala
index 9c07a05f..9686b87d 100644
--- a/dap2-service/src/main/scala/latis/service/dap2/HtmlCatalogEncoder.scala
+++ b/dap2-service/src/main/scala/latis/service/dap2/HtmlCatalogEncoder.scala
@@ -73,7 +73,7 @@ object HtmlCatalogEncoder {
 
   /** Provides a recursive HTML table representation of a Catalog's sub-catalogs */
   private[dap2] def subcatalogTable(catalog: Catalog, prefix: String = ""): IO[Text.TypedTag[String]] = {
-    val catalogs = Stream.emits(catalog.catalogs.toList)
+    val catalogs = Stream.eval(catalog.catalogs).flatMap(sub => Stream.emits(sub.toList))
     catalogs.evalMap { c =>
       val id = c._1.asString
       val cat = c._2
diff --git a/dap2-service/src/main/scala/latis/service/dap2/JsonCatalogEncoder.scala b/dap2-service/src/main/scala/latis/service/dap2/JsonCatalogEncoder.scala
index d437be6d..c6fe7f51 100644
--- a/dap2-service/src/main/scala/latis/service/dap2/JsonCatalogEncoder.scala
+++ b/dap2-service/src/main/scala/latis/service/dap2/JsonCatalogEncoder.scala
@@ -15,7 +15,8 @@ object JsonCatalogEncoder {
   /** Provides a JSON representation of a Catalog for a dap2 response. */
   def encode(catalog: Catalog, id: Option[Identifier] = None): IO[Json] =
     for {
-      cats <- catalog.catalogs.toList.traverse { case (id, cat) => encode(cat, Some(id)) }
+      subs <- catalog.catalogs
+      cats <- subs.toList.traverse { case (id, cat) => encode(cat, Some(id)) }
       dss  <- catalog.datasets.compile.toList.map(dss => dss.map(datasetToJson))
     } yield {
       val fields = List(