SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5064a68bd993b651a0a8526e1a75a1bc9b4fec5eedaf0b0add425cdb61010f49' 
  AND token = 'pfF3PFXAz0xsGr2LtgzIRZtBU67XaZ8clpAJBTSrF5o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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