SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7c7ef147d9ded26588051e888b642887f32bac43a07c69d5b8bc76efb029a0c7' 
  AND token = 'ajHWsw0XH/ZC1KjQ2REArqV+TT4bGJ8NEz8/z2qLo5c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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