SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ca36ee98395c0ca6197cc71bbc73c143b646826c385505c0e558cf6a88897f36' 
  AND token = 'CT+6nVmuetXba3nsDzDW9fzMGW6JZj18wZehpCaGfqQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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