SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db18a782fdcc3340921a2f4cf850ccbe7b7af9ec29370b3a6389b645a809b303' 
  AND token = '2ADJZ8p/cBPxc98HJFVjPDPbG6zF9K1hdFVRIla4zzo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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