SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76b38052d78e5540d34c58951554a3f93ebcd177457a350a562cbe68c0694696' 
  AND token = 'UeBxPSp4GwLm1msD7t4UFNelrcfc8GMJPaaasbnANzc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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