SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3d4672d8800b213caf37cb13e10f7fcea9abfa1144a127be100d74eaa6e2237' 
  AND token = 'D5GEhY5mQjSjpfVO+D7gtH6JHwdByR2Hn9YOJkV8T2M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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