SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91c20822f9fa495f6fe08a769937aa9a45f92830facf52c29aacea8e181a1202' 
  AND token = 'wARsXpRcN59e+2LNZaKvteDXrc96XxfZUqR6nYHUP3Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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