SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '821850d096fde77f6838ea72e3403ea41cc842cf96660c74d89eca39d51f232d' 
  AND token = 'C+fNEvjzZBQawwBLbv+SJHjKY7okq5AlnLGDjJHApiA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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