SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1908590173ae910af1dcda12433ac181568f0b3ccd920f5db212ad5c3e52c7b2' 
  AND token = 'pTrSvoVhkmha+WvMaEHqmsIbK7FH9yuHpYhE968ulLg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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