SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'df6d7c3929b266fa939001cafc3615d603580e6db0827c85fe29a26e8d19d091' 
  AND token = 'L0YTScQEINbVT2CGfMM0liJvI9wfa53niy2zLRITYTc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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