SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '387c1341cdbc01d565ca6d5a9a5b820237949445d53329f65079e865d56ffc30' 
  AND token = 'v+hXtAchSj/uqUkHywlGKpHtR3U1lhOjR+LZGGegnGo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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