SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3d50c43741993c5a92927279b09937c9af75df9cd6f5ff65aa6b1f54660d12de' 
  AND token = 'pjM78/3wuT8z4xsz+ytPHJKzTFZqKv0skmOCqUOWd+Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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