SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f542fc67a1d08fefcc13c67de6faeae96353bc85334068077fb93faca4dc3ba' 
  AND token = 'uK6JdieSX7lbWK9BCktxOloDUCmaK9CXHl+myTVtJf8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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