I recently searched for fares in Skyscanner. The cheapest ones were given by online travel agencies (eg: tripmonster, mytrip, etc.)
It's not the first time I used this type of agencies and one characteristic is the fact that the ticket is not issued immediately. It usually arrives within 24h.
I booked a couple of times and never had problems, but each time I buy I always wonder if the price is too good to be true or if it can be an error and I will never get my ticket with the initial fare.
Are these agencies reliable? Why do they keep these "offline" processing systems in an era where everything is being automated?