SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f48caa8dfe69a577454fe102b3e379e27a8d78edd5760d5893d8c61207096f2' 
  AND token = '1sumszmjqtDmItBZKZthzLTdMJhBChLuAjhl1gH2wZ8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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