SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4216840a4cbc2f8826a7e436f334c501e0dcb3a99539a03fda320b8f26a93e29' 
  AND token = 'xcDe4WGvyQUQhXBdmnJCsVwMZB9UOUCwRgYTMKhGkZ4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00008

JSON explain

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