Some of the biggest crypto exchanges are shutting out new users because they can't keep up with demand

A number of cryptocurrency exchanges have temporally halted on-boarding of new users.
Crypto-exchanges are under pressure to keep up with the breakneck growth of the booming digital coin market.

Cryptocurrency exchanges are experiencing growing pains as the market for digital coins explodes.

Exchanges have struggled to keep up with the breakneck growth of the crypto-market and eye-popping volumes. Exchanges have halted trading, experienced outages, and crashed during periods of high volumes and demand. Part of that pressure has been driven by hundreds of thousands of new market entrants.

Now, at least three cryptocurrency exchanges — Bittrex, Bitfinex, and CEX.io — have stopped onboarding new users altogether.

"We have received an enormous number of new account registrations over the past few weeks," said an alert on Bittrex, a US-based exchange."Unfortunately, we have to make a few upgrades to our support and backend systems to handle the increased traffic and load."

Bittrex is the third largest exchange by volume, according to data provider CoinMarketCap.com.

It's the same story for Hong Kong-based Bitfinex.

"Thank you for your interest in opening a Bitfinex account. However, due to extraordinary demand, new account creation has been temporarily paused," said an alert on Bitfinex.

Bitfinex said new account creation would be enabled by January 15. CEX.io, an exchange based in the United Kingdom, said the "enormous" amount of new users opening accounts on the exchange was making it difficult for the company to address a backlog of other technical issues on the site.

"Every day, an enormous number of users registers on our exchange, which we are extremely excited about," the company wrote in a blog post dated December 21. "At the same time, this has been putting additional pressure on our support and verification teams."

On the US-based exchange Kraken, it appears users can open a new account, but some cannot verify their account to buy and sell digital coins. This reporter was unable to verify his account when setting up a Kraken account, and other new users reported similar problems on Reddit. A representative from Kraken did not respond immediately to a message seeking comment.

Kraken chief executive officer Jesse Powell told Business Insider in November the firm was actively hiring new developers to build out its infrastructure to better handle record trading volumes.

Global cryptocurrency markets are now seeing daily trading volumes similar to the New York Stock Exchange.

Twenty-four-hour trade volume in the cryptocurrency market soared above $50 billion earlier in December, which is on par with trading activity on the New York Stock Exchange. The milestone illustrates just how hot the market has become in 2017.

Investors have flocked to the crypto-market to capture its eye-catching returns. Bitcoin, the largest cryptocurrency by market capitalization, has grown by about 1,400% against the dollar in 2017. A boom in so-called initial coin offerings, an crypto twist on the initial public offering process, has created a raft of other digital assets for investors to speculate on. There are now more than 1,300 cryptocurrencies in circulation,according to CoinMarketCap.com.