SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a54f6f3377b2f75e16cd1d05c55dfef28b8d2e2801727979c86d2b6baa04f22b' 
  AND token = 'jhJp1nmzHGg2Vb9Qhb+VOlz4rr0ZaBRLgJ5cMvzcfV4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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