SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8c349283b20d8e49d0b3daa27a97b6b2596a23fdf461f6d852018f25c171fdc' 
  AND token = 'VCLfOvSsxlVGCorokY/NkUDoTxTujjmfGrMTFnxw93E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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