SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '83db96229c309b8d3472c0cb6f1aeadd52e1cf8148371135593e8769bcae5797' 
  AND token = '6jDBAmi32RDbEh/p+EPx+HdKFtptK4wM5bqNsQjNOmM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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