SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5666acc3d80b2ef66d7df3d523f6b527785cd3e7ffbfc478e5c84ab60ea0549c' 
  AND token = 'fxjxkZlK2+YevsZBZuAKpChlaM6PP/JEZ1wxvP4YQDg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}