SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db921b648579fe5807bb835229514dc378faf65a69763d816d8e3384fd55a5b0' 
  AND token = '8DYeZEz+TCp7I8olbjPiAzi1JTNBu9z5TvphJ+xxEug=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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