diff --git a/src/Index/AbstractAggregateIndex.php b/src/Index/AbstractAggregateIndex.php
index ca4b7d4..a5826ab 100644
--- a/src/Index/AbstractAggregateIndex.php
+++ b/src/Index/AbstractAggregateIndex.php
@@ -107,42 +107,40 @@ abstract class AbstractAggregateIndex implements ReadableIndex
     public function getDefinitions(): \Generator
     {
         foreach ($this->getIndexes() as $index) {
-            yield $index->getDefinitions();
-        }
-    }
-
-    /**
-     * Returns an associative array [string => Definition] that maps fully qualified symbol names
-     * to global Definitions
-     *
-     * @return Definition[]
-     */
-    public function getGlobalDefinitions(): array
-    {
-        $defs = [];
-        foreach ($this->getIndexes() as $index) {
-            foreach ($index->getGlobalDefinitions() as $fqn => $def) {
-                $defs[$fqn] = $def;
+            foreach ($index->getDefinitions() as $fqn => $definitions) {
+                yield $fqn => $definition;
             }
         }
-        return $defs;
     }
 
     /**
-     * Returns the Definitions that are in the given namespace
+     * Returns a Generator providing an associative array [string => Definition]
+     * that maps fully qualified symbol names to global Definitions
+     *
+     * @return \Generator providing Definitions[]
+     */
+    public function getGlobalDefinitions(): \Generator
+    {
+        foreach ($this->getIndexes() as $index) {
+            foreach ($index->getGlobalDefinitions() as $fqn => $definition) {
+                yield $fqn => $definition;
+            }
+        }
+    }
+
+    /**
+     * Returns a Generator providing the Definitions that are in the given namespace
      *
      * @param string $namespace
-     * @return Definitions[]
+     * @return \Generator providing Definitions[]
      */
-    public function getDefinitionsForNamespace(string $namespace): array
+    public function getDefinitionsForNamespace(string $namespace): \Generator
     {
-        $defs = [];
         foreach ($this->getIndexes() as $index) {
-            foreach ($index->getDefinitionsForNamespace($namespace) as $fqn => $def) {
-                $defs[$fqn] = $def;
+            foreach ($index->getDefinitionsForNamespace($namespace) as $fqn => $definition) {
+                yield $fqn => $definition;
             }
         }
-        return $defs;
     }
 
     /**
diff --git a/src/Index/Index.php b/src/Index/Index.php
index ffd5941..9130246 100644
--- a/src/Index/Index.php
+++ b/src/Index/Index.php
@@ -107,28 +107,29 @@ class Index implements ReadableIndex, \Serializable
     }
 
     /**
-     * Returns an associative array [string => Definition] that maps fully qualified symbol names
-     * to global Definitions
+     * Returns a Generator providing an associative array [string => Definition]
+     * that maps fully qualified symbol names to global Definitions
      *
-     * @return Definition[]
+     * @return \Generator providing Definitions[]
      */
-    public function getGlobalDefinitions(): array
+    public function getGlobalDefinitions(): \Generator
     {
-        return $this->globalDefinitions;
+        foreach ($this->globalDefinitions as $fqn => $definition) {
+            yield $fqn => $definition;
+        }
     }
 
     /**
-     * Returns the Definitions that are in the given namespace
+     * Returns a Generator providing the Definitions that are in the given namespace
      *
      * @param string $namespace
-     * @return Definitions[]
+     * @return \Generator providing Definitions[]
      */
-    public function getDefinitionsForNamespace(string $namespace): array
+    public function getDefinitionsForNamespace(string $namespace): \Generator
     {
-        return isset($this->namespaceDefinitions[$namespace])
-            ? $this->namespaceDefinitions[$namespace]
-            : []
-        ;
+        foreach ($this->doGetDefinitionsForNamespace($namespace) as $fqn => $definition) {
+            yield $fqn => $definition;
+        }
     }
 
     /**
@@ -141,7 +142,7 @@ class Index implements ReadableIndex, \Serializable
     public function getDefinition(string $fqn, bool $globalFallback = false)
     {
         $namespace = $this->extractNamespace($fqn);
-        $definitions = $this->getDefinitionsForNamespace($namespace);
+        $definitions = $this->doGetDefinitionsForNamespace($namespace);
 
         if (isset($definitions[$fqn])) {
             return $definitions[$fqn];
@@ -314,4 +315,18 @@ class Index implements ReadableIndex, \Serializable
 
         return $fqn;
     }
+
+    /**
+     * Returns the Definitions that are in the given namespace
+     *
+     * @param string $namespace
+     * @return Definition[]
+     */
+    private function doGetDefinitionsForNamespace(string $namespace): array
+    {
+        return isset($this->namespaceDefinitions[$namespace])
+            ? $this->namespaceDefinitions[$namespace]
+            : []
+        ;
+    }
 }
diff --git a/src/Index/ReadableIndex.php b/src/Index/ReadableIndex.php
index 0c5efca..8d4e1ca 100644
--- a/src/Index/ReadableIndex.php
+++ b/src/Index/ReadableIndex.php
@@ -38,20 +38,20 @@ interface ReadableIndex extends EmitterInterface
     public function getDefinitions(): \Generator;
 
     /**
-     * Returns an associative array [string => Definition] that maps fully qualified symbol names
-     * to global Definitions
+     * Returns a Generator providing an associative array [string => Definition]
+     * that maps fully qualified symbol names to global Definitions
      *
-     * @return Definitions[]
+     * @return \Generator providing Definitions[]
      */
-    public function getGlobalDefinitions(): array;
+    public function getGlobalDefinitions(): \Generator;
 
     /**
-     * Returns the Definitions that are in the given namespace
+     * Returns a Generator providing the Definitions that are in the given namespace
      *
      * @param string $namespace
-     * @return Definitions[]
+     * @return \Generator providing Definitions[]
      */
-    public function getDefinitionsForNamespace(string $namespace): array;
+    public function getDefinitionsForNamespace(string $namespace): \Generator;
 
     /**
      * Returns the Definition object by a specific FQN