Scaling Databases at Activision [pdf](static.sched.com)

  -- setup
  postgres=# create table user_table(user_id int);
  CREATE TABLE
  postgres=# create table resources_table(resource_id int, user_id int);
  CREATE TABLE
  postgres=# insert into user_table values(1);
  INSERT 0 1

  Tran 1:
  postgres=# BEGIN TRANSACTION ISOLATION LEVEL REPEATABLE READ;
  BEGIN
  postgres=# select * from user_table where user_id = 1;
 user_id 
  ---------
       1
  (1 row)

  Tran 2:
  postgres=# BEGIN TRANSACTION ISOLATION LEVEL REPEATABLE READ;
  BEGIN
  postgres=# select * from resources_table where user_id = 1;
   resource_id | user_id 
  -------------+---------
  (0 rows)
  postgres=# delete from user_table where user_id = 1;
  DELETE 1
  postgres=# commit;
  COMMIT

  Tran 1:
  postgres=# insert into resources_table values (1,1);
  INSERT 0 1
  postgres=# commit;
  COMMIT

  Data at the end:

  postgres=# select * from resources_table;
   resource_id | user_id 
  -------------+---------
             1 |       1
  (1 row)

  postgres=# select * from user_table;
   user_id 
  ---------
  (0 rows)