SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'de420731b9326751105368ec401ddb447c4be4ca40c00ecad538f7ec93ce4bc6' 
  AND token = '1x/SrTvvlD7H/MGoMqb7W+wV69TJjZXDZsQcDn/CnYI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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