SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6a4802fdcb59b3fcb7658551464362b2b21d0c9a371747e42f058de1b653f8f' 
  AND token = 'gCOd1qQU5YGzAWToI9Gj7bB3gCJDD3KSimO2bN5AcOA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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