SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '999e6f148bd84bd997c949f193a87f795698419ceec4e388603e5e8fe633829e' 
  AND token = 'L7ERaynKlkcgZHeIuBYyfrZSoIBsoNdGcifn921f6mQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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