SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81b21e749fd23d0141d97792fe92439aef2d09e848c04689f472b7498f8b329f' 
  AND token = 'a/sEy1vZ8OtxuYKjVO+maCA5cFZAgDljM8LymwGEfBw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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