SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c350727fad08efeb85d0ce54b8aef305584b08daf7b872719631362eb0e2cb30' 
  AND token = 'OAvIe8Hh7zqB38SKQrtWd0sGgfgA4tyZPDYCjPiu+2Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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