SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '57712938699d519d7d5f02d8d1e4aab0842cd32ad9d8dd75a850aa35b556eae3' 
  AND token = 'Ips+vj2fXZ7mw0ZlBgVe5YQRv3zuHFy/bg0ffgsp6TY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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