SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15d16cfb892367a8e93569144c56bffb9a90cdd08131bafd9e302e4fb7646c76' 
  AND token = 'XKXL69aJXqjCsLrPQq4hzp+2FbPajxgPm/rTUVZCDyk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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