SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f768f1f1924e9ba2b1059a4b5f362820a232d371681a9eeae4f1e779c8e95043' 
  AND token = 'fHBUzfCXXt/h6mwHh+zl3kAi4BjVhWEp1tOzqlcP3tg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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