SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '256b430d4d64215a394524c0deb25cbb245b004d0e6dd92700e588ea7cd7f661' 
  AND token = 'z75hS8SUQfFsTvFoO8pvXHystLkl2ZZxGsDnI9gDvqg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}