SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78715c246ce237e2d41cf98ade21bda158021d66f1b21c1e5025b100de134dee' 
  AND token = 'yAjlfS32aVa+koEPC07fE+7JMQfTTQuNfKLxvPTTkq0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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