SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5a5d33b2a398926ffcc5dff636bdc945a3796ce1ed7c7c89e1b834154e3b8e3' 
  AND token = 'krUn/0fi6AqESw8LZdYWXVZBWWshP+nOvxtuOsEb2ZI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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