SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18b2666c83ffabd7f327b497ad9390fdbc909b1d747982b54408f133641c4572' 
  AND token = '8lhmENHFmfjdy0jP8xqRitzQMxPz4+9Xm/w/hVK7gDU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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