SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8f4f27c4e9e1346688b9ec0f8737655680b0e33704adf5d126e532130a72c6c' 
  AND token = 'K9XeF6ZYcDmWPBn03MM6gQ/qXxiFnVu7wgJ2pm+xYSg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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