SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8797fa3fc6f696f21332feb4ab6facbf6e70dddbaa509d1f1ab64e7ef3d8e4e5' 
  AND token = 'sZx4wfZpVRtQP9WDpvVWh46jYrsmUuMzvEA2pr/GwNM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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