SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '767ca40304d90a99e0562e506577dcf968735abbf3e5681579417cafcb704772' 
  AND token = '55mUJhjfjDnRD3LU1KgMNkCu3xihqaJAvQSI/Ke+IBc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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