SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a89c71db711fe445453399414da4810d6970b826623aa82b6b13b122fdf68351' 
  AND token = '8DQa2HUdmYAw1ViNsuxLigCBHMpkw0t0zZd3cv73TSI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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