diff --git a/config/application.rb.dist b/config/application.rb.dist
index b54a357..9270b0c 100644
--- a/config/application.rb.dist
+++ b/config/application.rb.dist
@@ -18,6 +18,8 @@ require "rails/test_unit/railtie"
 # you've limited to :test, :development, or :production.
 Bundler.require(*Rails.groups)
 
+require_relative '../lib/default_settings_strategy'
+
 module FixinMe
   class Application < Rails::Application
     # Initialize configuration defaults for originally generated Rails version.
@@ -39,6 +41,9 @@ module FixinMe
     config.action_dispatch.rescue_responses['ApplicationController::AccessForbidden'] = :forbidden
     config.action_dispatch.rescue_responses['ApplicationController::ParameterInvalid'] = :unprocessable_entity
 
+    # Set default migrations parameters.
+    config.active_record.migration_strategy = DefaultSettingsStrategy
+
     # SETUP: Below settings need to be updated on a per-installation basis.
     #
     # Set host to be used by links generated in mailer templates.
diff --git a/db/migrate/20230309185340_create_users.rb b/db/migrate/20230309185340_create_users.rb
index 1efb52e..25f32c7 100644
--- a/db/migrate/20230309185340_create_users.rb
+++ b/db/migrate/20230309185340_create_users.rb
@@ -1,11 +1,11 @@
-class CreateUsers < ActiveRecord::Migration[7.0]
+class CreateUsers < ActiveRecord::Migration[8.1]
   def change
     create_table :users do |t|
       t.string :email, null: false, limit: 64
       t.integer :status, null: false, default: 0
 
-      t.timestamps null: false
+      t.timestamps
     end
-    add_index :users, :email, unique: true
+    add_index :users, :email
   end
 end
diff --git a/db/migrate/20230311220654_add_devise_to_users.rb b/db/migrate/20230311220654_add_devise_to_users.rb
index 9ee005b..ad6c38d 100644
--- a/db/migrate/20230311220654_add_devise_to_users.rb
+++ b/db/migrate/20230311220654_add_devise_to_users.rb
@@ -1,4 +1,4 @@
-class AddDeviseToUsers < ActiveRecord::Migration[7.0]
+class AddDeviseToUsers < ActiveRecord::Migration[8.1]
   def change
     change_table :users do |t|
       ## NOTE: commented fields left for reference/inclusion in future migrations
@@ -34,8 +34,8 @@ class AddDeviseToUsers < ActiveRecord::Migration[7.0]
       # t.integer :failed_attempts, default: 0, null: false 
     end
 
-    add_index :users, :reset_password_token, unique: true
-    add_index :users, :confirmation_token, unique: true
+    add_index :users, :reset_password_token
+    add_index :users, :confirmation_token
     # add_index :users, :unlock_token, unique: true
   end
 end
diff --git a/db/migrate/20230602185352_create_units.rb b/db/migrate/20230602185352_create_units.rb
index d615c97..2e7a9a6 100644
--- a/db/migrate/20230602185352_create_units.rb
+++ b/db/migrate/20230602185352_create_units.rb
@@ -1,4 +1,4 @@
-class CreateUnits < ActiveRecord::Migration[7.0]
+class CreateUnits < ActiveRecord::Migration[8.1]
   def change
     create_table :units do |t|
       t.references :user, foreign_key: {on_delete: :cascade}
@@ -7,8 +7,8 @@ class CreateUnits < ActiveRecord::Migration[7.0]
       t.decimal :multiplier, null: false, precision: 30, scale: 15, default: 1.0
       t.references :base, foreign_key: {to_table: :units, on_delete: :cascade}
 
-      t.timestamps null: false
+      t.timestamps
     end
-    add_index :units, [:user_id, :symbol], unique: true
+    add_index :units, [:user_id, :symbol]
   end
 end
diff --git a/db/migrate/20250104194343_create_quantities.rb b/db/migrate/20250104194343_create_quantities.rb
index 59c98b5..1a70d32 100644
--- a/db/migrate/20250104194343_create_quantities.rb
+++ b/db/migrate/20250104194343_create_quantities.rb
@@ -1,4 +1,4 @@
-class CreateQuantities < ActiveRecord::Migration[7.2]
+class CreateQuantities < ActiveRecord::Migration[8.1]
   def change
     create_table :quantities do |t|
       t.references :user, foreign_key: {on_delete: :cascade}
@@ -6,12 +6,12 @@ class CreateQuantities < ActiveRecord::Migration[7.2]
       t.text :description
       t.references :parent, foreign_key: {to_table: :quantities, on_delete: :cascade}
 
-      t.timestamps null: false
+      t.timestamps
 
       # Caches; can be computed from other attributes
       t.integer :depth, null: false, default: 0
       t.string :pathname, null: false, limit: 511
     end
-    add_index :quantities, [:user_id, :parent_id, :name], unique: true
+    add_index :quantities, [:user_id, :parent_id, :name]
   end
 end
diff --git a/db/migrate/20250121230456_create_readouts.rb b/db/migrate/20250121230456_create_readouts.rb
index 25cf6ca..208f6f4 100644
--- a/db/migrate/20250121230456_create_readouts.rb
+++ b/db/migrate/20250121230456_create_readouts.rb
@@ -1,4 +1,4 @@
-class CreateReadouts < ActiveRecord::Migration[7.2]
+class CreateReadouts < ActiveRecord::Migration[8.1]
   def change
     create_table :readouts do |t|
       t.references :user, null: false, foreign_key: {on_delete: :cascade}
@@ -10,8 +10,7 @@ class CreateReadouts < ActiveRecord::Migration[7.2]
       #t.references :collector, foreign_key: true
       #t.references :device, foreign_key: true
 
-      t.timestamps null: false
+      t.timestamps
     end
-    add_index :readouts, [:quantity_id, :created_at], unique: true
   end
 end
diff --git a/lib/default_settings_strategy.rb b/lib/default_settings_strategy.rb
new file mode 100644
index 0000000..26cc12b
--- /dev/null
+++ b/lib/default_settings_strategy.rb
@@ -0,0 +1,32 @@
+class DefaultSettingsStrategy < ActiveRecord::Migration::DefaultStrategy
+  # Without `:if_not_exists`/`:if_exists` options it's impossible to change
+  # migration status once migration fails partially. If `up` migration creates
+  # some, but not all objects, its status is not updated from `down` to `up`.
+  # Then it's impossible to migrate: a) up - due to `already exists` errors and
+  # b) down - due to migration status.
+  # Using `force: :cascade` does nothing on MySQL, so `force:` is useless.
+  # Adding `null: false` here somehow does not show up in schema files, be careful!
+  # TODO: add_foreign_key {on_delete: :cascade} ?
+  DEFAULTS = {
+    add_check_constraint: {if_not_exists: true},
+    add_column:           {if_not_exists: true},
+    add_foreign_key:      {if_not_exists: true},
+    add_index:            {if_not_exists: true, unique: true},
+    # Timestamps are by default `null: false, precision: true`.
+    add_timestamps:       {if_not_exists: true},
+    create_table:         {if_not_exists: true},
+    drop_table:               {if_exists: true},
+    remove_check_constraint:  {if_exists: true},
+    remove_column:            {if_exists: true},
+    remove_foreign_key:       {if_exists: true},
+    remove_index:             {if_exists: true},
+    remove_timestamps:        {if_exists: true},
+  }
+  DEFAULTS.default = {}
+  DEFAULTS.freeze
+
+  def method_missing(method, *args, **kwargs, &)
+    conflicts = kwargs.has_key?(:force) ? [:if_not_exists, :if_exists] : []
+    super(method, *args, **DEFAULTS[method.to_sym].except(*conflicts).merge(kwargs), &)
+  end
+end