SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7f3c4bd5ce73998e8fcad99487293cfd27d0362fb9e99638dad61b8887e4309d' 
  AND token = 'OQBZcVuUz7lCc7ezTwU96vVUiKq6sWpWB4qKfa+qpO0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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