SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c2588cd73305961c35c51ab534adb3b402b786768e56125ec46a277fbd8ead1' 
  AND token = 'EclnwfrRSyqhgTgXMppQBkYkK91mqFk9v1TVEg5iXHo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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