SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '921d9359fca489a5b1fd80ffa8e8ed65937a0ff522a74a77fc0cde7d584d6e29' 
  AND token = 'hlB/zz2MJ2nUBT/qBwvD25jvbEL+ouCeRnNnhKZy+nc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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