SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50301f643a827d209bb6787cc438a663b11b731c9f473018cdbb56f044bb5a20' 
  AND token = '478/Y+0ST9MV9OM7XaprDH6EwHdcb4Xdb1BIcc+G80A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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