ActiveRecord methods(find_by, find etc) not working when using use_transactional_fixtures = true in rspec

Question

I am trying to move from use_transactional_fixtures = false to use_transactional_fixtures = true on my ROR application. Many cases are failing after setting use_transactional_fixtures = true in RSpec config. On further digging I came to find that the Active record query were not reading from transactions.

Example

   before(:all) do
     @user = User.first
   end
...
   describe 'POST #create' do
    context 'with valid params' do
      it 'creates a new HighScore' do
        post :create, high_score: { game: 'Test Game', score: 200, user_id: @user.id }
        parsed_response = JSON.parse(response.body)
        expect(@user.high_scores.find_by(id: parsed_response[:highscore_id])).to be_instance_of(HighScore)
      end
    end
  end

users table data before test starts

id	first_name	last_name	email
1	Test	Account	[email protected]

high_scores table before test starts

id	game	score	user_id
1	One	100	1

The issue with this is @user.high_scores.find_by(id: parsed_response[:highscore_id]) returns

nil

But the expected response is:-

#<HighScore id: 2, game: "Test Game", score: 200, created_at: "2022-04-11 10:36:39", updated_at: "2022-04-11 10:36:39", user_id: 1>

HighScore.all returns the value which is persisted in database before the test started i.e

#<HighScore id: 1, game: "One", score: 100, created_at: "2022-04-07 10:36:39", updated_at: "2022-04-07 10:36:39", user_id: 1>

The controller methods are all working and there is no issue with respect to creation of object. These cases were working fine when transactional_fixtures were set to false.

Versions
Rails 4.2.11.3
ruby 2.6.9
RSpec 3.7
  - rspec-core 3.7.1
  - rspec-expectations 3.7.0
  - rspec-mocks 3.7.0
  - rspec-rails 3.7.2
  - rspec-support 3.7.1

I need someone to help me out on what is the cause that queries are not getting executed on transactions but rather on tables.