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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c0f878341f6c23b052a833dc56888893969b9877a7faba37717e4d1815341fb5' 
  AND token = '5iDc3/ynnDbvOKieKUis7XCMJRuxelFHQfkkwsyckso=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}