SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe786fbaa4e93834c05cfa68d9ec8492609ad856ee70962917950ee28d3f76e1' 
  AND token = 'fC+qt+sTXWSmLgZ6POetBMFjsVFfakJZGfGGnFsgETU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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