SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a5a730f2ea6309cc22cbd3f509355f9c66d5010930e54f504755618da821c5a' 
  AND token = 'UDXiQ7fkUwYiz8mGlSTEk+PcXn9ahHZhCk7hMa93Q3w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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