SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '21257e4c57b6c7a7c6463f9f367f95a874378a9ebb0d5e5d6066219522d39cdd' 
  AND token = 'XIA1wsuxh5FZEfZKqT+tveYmsBKMOn4L3fl80yYW2Rg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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