SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a4c7ebeb684a161c4f347cf023446f615262ff8079b5c3040bd562b7d14c6f75' 
  AND token = 'f53UnjpnjzSPy/Y2VEKydw3zPwl0q3lklBGIYoLBVwk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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