SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ce5481b94a6801284606ef1f644b6ee0fe63433f26d4b32af4cdfab0869e125' 
  AND token = 'MMPaXR6h0PXCfwqOXwzggkijmjIqQfFhIXlqVM0rMgg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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