SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2f6c36eefdc10863a345b27fc338d2f942d4d8d873af7a587a072c977cfae446' 
  AND token = 'Im5hDwBsij8WMfRhmQnKblmdpb2xuO+POZ0neL2vwiY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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