SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '208fd5c9420fb9c13daabab529d219e1ea087bd41adfa6915bd6798bd7af8a46' 
  AND token = 'lF9YVpxwlnxZMbAuddDKevOYrWF02zw8Z2kaBxDGhkQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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