SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = 'a268f98373f401ab2d577a87424f14a659557996a34619c2ca5df543d56c3578' 
  AND token = '7raUkSrtGoeSVmkf1UayVITc56dZrQQQwGeHoHne/DE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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