SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78a38929041b2c65f4eb42cb27ee0f2d8cac68a8323fae44fde44e2dfdc3f564' 
  AND token = 'XkTavlfEn/CLIrnbrlxdlQpwKiDrYrINRKcS3O+IjLY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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