SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b2ca3a778f86f38244a0f60f5a4bdeff44bb89fdf106e1b5cdb5d5a077521000' 
  AND token = 'BzkRupHDx4WOluXgqIz6zIaBDJjVuU3DohPQnbJ33HM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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