SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '336e5513780279a589b5b650167ddb6cc75f8968fbaf06130edb3594b40ee74d' 
  AND token = 'UVO/qLKUn51iK7M/Ag5d8JVgfVXViS1Up+GUG9UAwmg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}