SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '12c4ddb2f40841c959d36b8208349d63cf251ee671fad7b825dede0c98c8536f' 
  AND token = '6MuElzx3igzi/xxqsou52qGoCw0GpUm6ztRUxz0HwQU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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