SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'd58dcaa882b3e1769a91fa5ef1bf18b980cee8c378d2efdd15135392443b062e' 
  AND token = 'eQdtcmEteCRx8JWnQIJ9Q8jYEU8D6sIuOlOOG5tZbkQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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