SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '621af7c4c5df7d5a7648bf88e383816099042b19e83c1dea7bd75372ebdde081' 
  AND token = 'iT7t/iblGxfxRc4IMpsPJYk1Md2EwV65ylKox2bgfBg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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