SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6c43db31960ba6c605d1d242f38d914566da5a442f3485b1d47a74d21dc0852' 
  AND token = 'CMWWWoL9poL+PYS1Vmen3T8THWzoRXv1Vj3qBqgdcFM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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