SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e0fcb66dc100f5d4cd0ae0dd7a8351b3748e327658c643902420f259bd178850' 
  AND token = 'nJnq4jOfzypwUfPYKap52VaQkH8PirncZ9EoU8S8RCk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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