SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c546df88a6af0c6119539e628e074d800bbb66a2148da756bad62499f3348fe' 
  AND token = 'DQBzUQXLhCLiLUFs6nSpJhKzH/NOCwyJKaRC8Qa6sR4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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