SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a21912c57de4f9e703cec8b43ffd6497dfc0e255d47267fca7c1ea77f0f11978' 
  AND token = 'V7o59gXglj1Tn0Giy+ahSt/3IKz6VuqitB9w/4Jrlt4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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