SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '314b252520c7016a07cbf311c906c183662820908c45f4fc1d73b2dec714e1e8' 
  AND token = '6nUydEi0IyKwqNQJWRTnNsQ1CzmHQwo1ID3QjzL88NM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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