SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2f6d6620a9f147791e97c1500fe8abe51cebc4a0a81bff1b5032ba17d258b3af' 
  AND token = '6qKuiNeMxttSTERS8152iP11yp/SkGlxx7iJsH8zGqA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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