SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df39bf6d420389242b25a379195bbefd04196ad96147afb918f88c8c7adc48f9' 
  AND token = 'IlAN0VutFblS2D0UveHmqs3amb1CZYChjRX29teEFc4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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