With the market hovering at historic highs, it might seem smarter to sell your high-growth stocks, lock in the gains, and buy some conservative income plays instead.

However, it would be foolish to ignore high-growth stocks altogether, since they could outperform the market over the long term. Here are three growth stocks I'd still consider buying in this frothy market: Shopify (NYSE:SHOP), Baozun (NASDAQ:BZUN), and Secoo (NASDAQ:SECO).

Shopify

Shopify provides an e-commerce platform that enables businesses to quickly design, set up, and run their online stores. It also helps companies process orders, payments, and shipments, build customer relationships, and leverage analytics to gauge a business' performance and needs.

A smartphone displaying a shopping cart icon.

Image source: Getty Images.

In the past, the bears claimed that Shopify's business model of one-stop e-commerce could be rendered obsolete by Amazon.com, which launched WebStore as a Shopify rival in 2010. Yet Shopify continued growing, and Amazon eventually shuttered WebStore and integrated Shopify's platform into its own marketplace.

Shopify has also been expanding its ecosystem with new features, like Shopify Pay, which lets merchants store a customer's payment information, as well as a point-of-sale card reader, a wholesale channel for buyers, and new APIs that allow developers to integrate Shopify's platform into their apps.

Shopify's revenue rose 95% in 2015 and another 90% in 2016. Wall Street expects 67% growth this year -- which is still impressive for a 13-year-old company. Shopify isn't profitable, but analysts expect its losses to narrow this year and lead to a full-year adjusted profit in 2018.

Shopify isn't a cheap stock at 21 times sales, which is well above the industry average of six for application software makers, but its solid sales growth, defensible niche, and march toward profitability could keep investors interested.

Baozun

Baozun is often called the "Shopify of China" because it applies the same business model to the Chinese market, where internet penetration rates remain lower and many brick-and-mortar retailers are offline.

A young woman places an online order with her smartphone.

Image source: Getty Images.

The bear thesis against Baozun was similar to the one against Shopify -- that bigger e-commerce companies like Alibaba (NYSE:BABA) could launch competing platforms and render it obsolete. But Alibaba is actually one of Baozun's top investors, and it's already integrated Baozun's platform into its Tmall and Taobao marketplaces.

But this doesn't mean that Baozun is immune from competition. For example, Tencent (NASDAQOTH:TCEHY) is expanding its e-commerce and payments features in WeChat, the top messaging app in China, which could enable vendors to connect with sellers without going through Alibaba or Baozun.

Baozun's revenue rose 64% in 2015 and 31% in 2016. Analysts expect Baozun's revenue to rise 20% this year. Those growth figures seem weaker than Shopify's, but Baozun beats Shopify in terms of profitability. Baozun's earnings rose 275% in 2016, and analysts expect 105% growth this year.

Baozun isn't cheap at 111 times trailing earnings, but its price-to-sales ratio of 4 looks more reasonable than Shopify's. Therefore, investors looking for a Shopify-like play but dislike Shopify's premium valuation should take a closer look at Baozun.

Secoo

Secoo is a smaller Chinese e-commerce player that specializes in luxury goods. It controls 25% of the upscale e-commerce market in China, and targets second-, third-, and fourth-tier cities that have growing income levels but aren't adequately served by top luxury brands.

Two young women shopping.

Image source: Getty Images.

Secoo's recent IPO was an embarrassing bust, mainly due to demand and valuation issues, and the stock now trades about 30% below its initial price of $13. The bears argue that Secoo's moat is narrow and that Alibaba, JD.com, and Tencent are all expanding into the luxury market, which could render a smaller niche player like Secoo obsolete.

However, Secoo's growth figures have been solid. Its total revenue rose 49% annually last year, and climbed another 30% in the first half of the year. Its registered users rose 42% annually to 15.1 million during the period, and its average customer spends over $500 per order. Secoo wasn't profitable in previous years, but its loss narrowed in 2016 and it actually reported a profit in the first half of the year.

Analysts haven't presented any growth estimates yet, so it's tough to gauge the company's near-term future. However, the stock's post-IPO sell-off has reduced its P/S ratio to just over 1, so its downside should be limited from current levels.

These stocks aren't for queasy investors

I personally own shares of Baozun and Secoo, and I'm thinking about buying Shopify, even though the stock is at an all-time high. But I still consider all three stocks speculative side bets that shouldn't replace the core holdings in your long-term portfolio.

Leo Sun owns shares of Amazon, Baozun, Tencent Holdings, and Secoo Holding Limited-ADR. The Motley Fool owns shares of and recommends Amazon, JD.com, and Shopify. The Motley Fool has a disclosure policy.