SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68df9733b9d9b21e3a2f5f84679d0b64340904c58f19c3a862bda48760307902' 
  AND token = 'YOTuJIsqKH5dagsECHlwKFIUJZhjqsFIV/mdQFv9AwA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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