SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c51b95abaeee38bdbcf5fb89808a01555356b5ff550b0cca28a6e3d6fbe32449' 
  AND token = 'HOmomv3fgRfL3DtypotnJwGY1xYuGndizf2EnGGXTTY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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