SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db98e7431c0868ba3ed6566ec3529108bed5256a4dcd4a167c0480f2bd0437c7' 
  AND token = 'RscsWVC2SdKEFCCkpZu8/SnEQNboxpsN4QdQqGgKmCo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}