SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75423c598d17755f293d5df1ca856c98cbcadd6164d2bbe3026fd246558d2a76' 
  AND token = '/59R9c7VEhfdHcmwKgxE+voWZQj8+WKmjyMeVajziPo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00040

JSON explain

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