SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db21dba44b8a4a3e394a0ea8b2768416756e891efcaa8f23bbb5c5bee6d8d311' 
  AND token = 'TMSYiz7Z3oPI2rWrZVYv+fb0dTiWvR7FzPYyQzh4itA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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