SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '35df6aaa63424a3c35ecd3fde50ff256d295966297451b4e202779e691c29914' 
  AND token = 'Hmhe+WXmIiI/qBzPL8zSstJ1e5JRNxciMHPfGCSpIu8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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