diff --git a/app/models/archive.rb b/app/models/archive.rb
index 2f2f5c1b8..7ee93720f 100644
--- a/app/models/archive.rb
+++ b/app/models/archive.rb
@@ -3,6 +3,7 @@
 # Table name: archives
 #
 #  id             :bigint           not null, primary key
+#  key            :text             not null
 #  month          :date
 #  status         :string           not null
 #  time_span_type :string           not null
@@ -56,4 +57,15 @@ class Archive < ApplicationRecord
       "procedure-#{procedure.id}-mois-#{I18n.l(month, format: '%Y-%m')}.zip"
     end
   end
+
+  def self.find_or_create_archive(time_span_type, month, groupe_instructeurs)
+    create_with(groupe_instructeurs: groupe_instructeurs)
+      .create_or_find_by(time_span_type: time_span_type, month: month, key: generate_cache_key(groupe_instructeurs))
+  end
+
+  private
+
+  def self.generate_cache_key(groupe_instructeurs)
+    groupe_instructeurs.map(&:id).sort.join('-')
+  end
 end
diff --git a/app/services/procedure_archive_service.rb b/app/services/procedure_archive_service.rb
index 1b5bd86e3..b26757210 100644
--- a/app/services/procedure_archive_service.rb
+++ b/app/services/procedure_archive_service.rb
@@ -10,18 +10,7 @@ class ProcedureArchiveService
       .groupe_instructeurs
       .where(procedure: @procedure)
 
-    archive = Archive.for_groupe_instructeur(groupe_instructeurs).find_by(
-      time_span_type: type,
-      month: month
-    )
-    if archive.nil?
-      archive = Archive.create!(
-        content_type: type,
-        month: month,
-        groupe_instructeurs: groupe_instructeurs
-      )
-    end
-    archive
+    Archive.find_or_create_archive(type, month, groupe_instructeurs)
   end
 
   def collect_files_archive(archive, instructeur)
diff --git a/db/migrate/20210427124500_add_key_to_archives.rb b/db/migrate/20210427124500_add_key_to_archives.rb
new file mode 100644
index 000000000..08559a0dc
--- /dev/null
+++ b/db/migrate/20210427124500_add_key_to_archives.rb
@@ -0,0 +1,6 @@
+class AddKeyToArchives < ActiveRecord::Migration[6.1]
+  def change
+    add_column :archives, :key, :text, null: false
+    add_index :archives, [:key, :time_span_type, :month], unique: true
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 04a730a00..eefe0112f 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2021_04_27_112642) do
+ActiveRecord::Schema.define(version: 2021_04_27_124500) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -87,6 +87,8 @@ ActiveRecord::Schema.define(version: 2021_04_27_112642) do
     t.string "time_span_type", null: false
     t.datetime "created_at", precision: 6, null: false
     t.datetime "updated_at", precision: 6, null: false
+    t.text "key", null: false
+    t.index ["key", "time_span_type", "month"], name: "index_archives_on_key_and_time_span_type_and_month", unique: true
   end
 
   create_table "archives_groupe_instructeurs", force: :cascade do |t|
diff --git a/spec/factories/archive.rb b/spec/factories/archive.rb
index 8bdbb877e..41fbc2542 100644
--- a/spec/factories/archive.rb
+++ b/spec/factories/archive.rb
@@ -2,6 +2,7 @@ FactoryBot.define do
   factory :archive do
     time_span_type { 'everything' }
     groupe_instructeurs { [association(:groupe_instructeur)] }
+    key { 'unique-key' }
 
     trait :pending do
       status { 'pending' }