SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '812a4df875293abad5ded79396d032a13d366e1efed184692f11aa83d3d7de36' 
  AND token = '+EqQy7SKbcQYrejHyzAlJPevR7fz7cU8hHszwgFBuHU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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