SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f8871426c0531afb65eb37926f04d0ea461cb422bf9fe828672a54666d214f2' 
  AND token = 'bTyRNYyXpI278Ts2VfSzl3yXppXv+GHHLtvIK2NrWuw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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