SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b23ad1855d28e54b79199d371db1d64821b9f50ab08efad14d61480f6e670fa3' 
  AND token = '39Z6tvytjEFAJ+/4cqjSE5xL8wHBvXHsIdHZ+u9vBqM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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