SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9c781c10f2aad88c3604dca072eb86fec5ec7462733d3f96f19ba98e20120828' 
  AND token = 'XMxgrqstTElT0pXa5j+lLepF+nsLJ0XnJjbS73zhqtk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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