SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6723b591848a520d8ff0c96db359e406d27887641734191deea6403d5cb57fb' 
  AND token = 'UtBk1C1W83aBxv7EX97z044l5EvCpaeBXJHwwOFew3E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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