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The last time Starbucks did this, the stock plunged 30%

Starbucks is on a record-making streak heading into earnings
Starbucks is on a record-making streak heading into earnings

Starbucks shares are piping hot.

The stock has rallied 20% this year, already notching 21 all-time highs as of Thursday, its most records for the first four months of a year since 2012. However, after hitting a high in mid-April 2012, the coffee chain plunged more than 30% through July.

One chart watcher sees a similar setup this time.

"Here's a stock that looks great on the chart on a very long-term basis. Near term, it's getting a little extended, though," equity strategist Matt Maley said Wednesday on CNBC's "Trading Nation."

Starbucks has bounced 63% off its 52-week low set last June and has tripled the S&P 500's gains over the past six months.

"If you look at not just its daily RSI chart but its weekly RSI chart, it's getting very extended and it's now up to levels where it usually tops out," said Maley.

Starbucks' relative strength index, a measure of momentum, peaked above 80 two weeks ago. Any reading above 70 typically suggests overbought conditions. It now reads 66.

"When you get this much of a rally and get this extended, once you get past the earnings, it may get one more boost, but I think you're going to get an opportunity to buy at lower levels over the coming weeks, so I'd rather buy it on weakness than chase it up at these levels," he said.

Starbucks moved higher in extended trading Thursday after topping quarterly earnings expectations. Global comparable store sales came in slightly softer than anticipated at 3% growth compared with a 3.1% expected increase.  

Quint Tatro, founder and president of Joule Financial, says the earnings report could be the one to take Starbucks shares lower.

"Starbucks has gotten a little bit overcaffeinated here," Tatro said on the CNBC segment.  "Investors probably, again having gotten a little bit ahead of themselves, sell that. I would, however, agree that it's a buy on pullbacks."

Disclosure: Joule Financial holds SBUX on behalf of clients.