SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '342522127ff04382523d65cceb17224fe56999340fca780ee7e120b87700cde6' 
  AND token = '8JCRS7LaahVAwPyaX2K1wW7snEi+ZBrqFGPP9gPWpCU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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