SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5f37d4ddf7bcf7fa03871925795d0836cc38353fd9e1f8d71093cb300ad2ed5e' 
  AND token = '+CWuN3nbRAUfIi8TPVCPJwljwYIs1DvnjwPk7NwZvsw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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