diff --git a/dacite/types.py b/dacite/types.py
index 1bdd209..8ab61a9 100644
--- a/dacite/types.py
+++ b/dacite/types.py
@@ -102,7 +102,7 @@ def is_valid_generic_class(value: Any, type_: Type) -> bool:
     origin = get_origin(type_)
     if not (origin and isinstance(value, origin)):
         return False
-    type_hints = get_type_hints(type(value))
+    type_hints = cache(get_type_hints)(type(value))
     for field_name, field_type in type_hints.items():
         if isinstance(field_type, TypeVar):
             return (
@@ -121,6 +121,31 @@ def extract_init_var(type_: Type) -> Union[Type, Any]:
         return Any
 
 
+@cache
+def get_constraints(type_: TypeVar) -> Optional[Any]:
+    return type_.__constraints__
+
+
+@cache
+def is_constrained(type_: TypeVar) -> bool:
+    return hasattr(type_, "__constraints__") and get_constraints(type_)
+
+
+@cache
+def get_bound(type_: TypeVar) -> Optional[Any]:
+    return type_.__bound__
+
+
+@cache
+def is_bound(type_: TypeVar) -> bool:
+    return hasattr(type_, "__bound__") and get_bound(type_)
+
+
+@cache
+def is_generic_bound(type_: TypeVar) -> bool:
+    return is_bound(type_) and get_bound(type_) is not None and is_generic(get_bound(type_))
+
+
 def is_instance(value: Any, type_: Type) -> bool:
     try:
         # As described in PEP 484 - section: "The numeric tower"
@@ -164,13 +189,13 @@ def is_instance(value: Any, type_: Type) -> bool:
     elif isclass(type(type_)) and is_generic_alias(type(type_)):
         return is_valid_generic_class(value, type_)
     elif isinstance(type_, TypeVar):
-        if hasattr(type_, "__constraints__") and type_.__constraints__:
+        if is_constrained(type_):
             return any(is_instance(value, t) for t in type_.__constraints__)
-        if hasattr(type_, "__bound__") and type_.__bound__:
-            if isinstance(type_.__bound__, tuple):
-                return any(is_instance(value, t) for t in type_.__bound__)
-            if type_.__bound__ is not None and is_generic(type_.__bound__):
-                return isinstance(value, extract_generic(type_.__bound__))
+        if is_bound(type_):
+            if isinstance(get_bound(type_), tuple):
+                return any(is_instance(value, t) for t in get_bound(type_))
+            if is_generic_bound(type_):
+                return isinstance(value, extract_generic(get_bound(type_)))
         return True
     elif is_type_generic(type_):
         return is_subclass(value, extract_generic(type_)[0])