SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ecd5053966c9c3a62b4d29f380860df476fd2b9e872222a33c545499195cc621' 
  AND token = '5/tutMrAMxvp3aJWNI9hqDVhUvWAhKONNnodp6Vn8kA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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