I get the following intermittent test failure errors for some queries.

 ** (DBConnection.ConnectionError) connection not available and request was dropped from queue after 1102ms. This means requests are coming in and your connection pool cannot serve them fast enough. You can address this by:
     
       1. Ensuring your database is available and that you can connect to it
       2. Tracking down slow queries and making sure they are running fast enough
       3. Increasing the pool_size (albeit it increases resource consumption)
       4. Allowing requests to wait longer by increasing :queue_target and :queue_interval
     
     See DBConnection.start_link/2 for more information
     

How should I resolve this? I have three config files, test, dev and pre_prod. I don’t think increasing the pool size in pre_prod contributes to test execution.

dev.exs Config

config :my_app, MyApp.Repo,
   username: "postgres",
   password: "postgres",
   database: "my_app_dev",
   hostname: "localhost",
   show_sensitive_data_on_connection_error: true,
   pool_size: 10

pre_prod.exs Config

config :my_app, MyApp.Repo,
  username: "postgres",
  password: "postgres",
  database: "my_app_preprod",
  hostname: "db",
  show_sensitive_data_on_connection_error: true,
  pool_size: 10

test.exs Config

config :my_app, MyApp.Repo,
  username: "postgres",
  password: "postgres",
  database: "my_app_test#{System.get_env("MIX_TEST_PARTITION")}",
  hostname: "localhost",
  pool: Ecto.Adapters.SQL.Sandbox