diff --git a/pyteomics/proforma.py b/pyteomics/proforma.py
index 3a17f58..8763f1f 100644
--- a/pyteomics/proforma.py
+++ b/pyteomics/proforma.py
@@ -25,6 +25,7 @@
 from .mass import Composition, std_aa_mass, Unimod, nist_mass, calculate_mass, std_ion_comp, mass_charge_ratio
 from .auxiliary import PyteomicsError, BasicComposition
 from .auxiliary.utils import add_metaclass
+from .auxiliary.utils import memoize
 
 try:
     import numpy as np
@@ -343,6 +344,7 @@ def load_database(self):
             return obo_cache.resolve("http://www.unimod.org/obo/unimod.obo")
         return Unimod()
 
+    @memoize(maxsize=10000)
     def resolve(self, name=None, id=None, **kwargs):
         strict = kwargs.get("strict", self.strict)
         exhaustive = kwargs.get("exhaustive", True)
@@ -398,6 +400,7 @@ def __init__(self, **kwargs):
     def load_database(self):
         return load_psimod()
 
+    @memoize(maxsize=10000)
     def resolve(self, name=None, id=None, **kwargs):
         if name is not None:
             defn = self.database[name]
@@ -443,6 +446,7 @@ def __init__(self, **kwargs):
     def load_database(self):
         return load_xlmod()
 
+    @memoize(maxsize=10000)
     def resolve(self, name=None, id=None, **kwargs):
         if name is not None:
             defn = self.database[name]
@@ -562,6 +566,7 @@ def get_mass_from_term(self, term, raw_mass):
              "Only a rough approximation is available.") % (term, ))
         return rough_mass
 
+    @memoize(maxsize=10000)
     def resolve(self, name=None, id=None, **kwargs):
         if name is not None:
             term = self.database[name]
@@ -613,6 +618,7 @@ def parse_identifier(self, identifier):
         """
         return identifier, None
 
+    @memoize(maxsize=10000)
     def resolve(self, name=None, id=None, **kwargs):
         defn = None
         for resolver in self.resolvers: