It's been 30 minutes and the order has not yet been filled. So I canceled the order.
How long does it take for an order to be filled?
It will take time especially if the price is not within the range anymore.
If you want a fast trade then better to choose the buying/selling price in the next 5 on the list, and with this you can easily filled your trade without waiting any longer. Your trade will always depend on the price, and the buyer and seller level, so make sure to check it before you place a trade.
^That is exactly what I am going to say.
If you cancel your order after 30 minutes because it had not been filled, it is possible that the market conditions were not favorable for your specific order at that time. It is generally a good practice to monitor the market and consider adjusting your order if it has not been filled within the reasonable time frame that you expected.
Probably I think if you have any specific concerns or questions about a particular order on Coinbase, I recommend reaching out to their customer support for more accurate and up-to-date information regarding your specific situation.