text: -- Positions
  CREATE TABLE IF NOT EXISTS `position` (
    id INT NOT NULL AUTO_INCREMENT,
    userId INT NOT NULL,
    base CHAR(3) NOT NULL, -- a currency name an user hold
    qty BIGINT NOT NULL, -- a user's currency position quantity
    createdAt BIGINT NOT NULL,
    updatedAt BIGINT NOT NULL,
    PRIMARY KEY (id)
  ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
  ALTER TABLE position ADD INDEX idx_position_userId(`userId`);
  ALTER TABLE position ADD UNIQUE idx_position_userId_base(`userId`,`base`);
  