SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3121489a0856e5173907828c0df10b038544c1cccbc8e9b4e958824700d3678d' 
  AND token = '5NMVyOogZZLuPYG7AupLqhHYfwAJ5A6x+mBMY4r6SAw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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