SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9c4e12dd283d71a3b60a789a51fed1968e604c0dac42d027595795bfbbfe676' 
  AND token = '9R2DeM2JcgBSFucdJHmFWvVZcQOpRsajhF55mLvyCTU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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