SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a5ddf3fa1976813cf179f2fff95d6a95fabc44229132bfc707ee435e69ea5b31' 
  AND token = '9ekzh8gdrCA9QkRQHeuDzyw25hyneXZUdWnqaTEpESQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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