SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f9a90c7b16a7b1f72d1784d9d0a06834220fb80dadc38c0a8845f758a281f39' 
  AND token = 'sUwZD9nn96W26mlJQTK3qgiw/XOMu6wIKC3IWR5bRKs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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