SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '935811be57613cfc224d489efc55d35b52849b124f81600d8c3e3d989fd86750' 
  AND token = '3Y7YED9BUcjqaTHzUvPbOo6Lsmvh2RwLBpCBGicgn+Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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