SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a54af83fac54187d63c11bb162907f6427bbccf38b2760d3f4aaa3a1d3b8169' 
  AND token = 't+C8vmXZl8D4uPG+xUZ5Lu0Oj4ApvRO1Dc+gSzHpqj0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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