SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '73d4fe533b45d494343e2a5f78626527ced1ef6969b8b67b3e1e7e4959547166' 
  AND token = '0+U0mKiYFe8/3qQ7OmSKsqhoZ6DW+92SbHcPxyixq3c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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