SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6cef551adad927f4251158157e29a79eb20cea19fccedd48782b713ac0dcba8' 
  AND token = 'BMBm9alZ7uZYG50Uu5YQELjvbc4Ct/escb/g9QXeztM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}