SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '815112a3493b4e53f31071e635f7a7fc10370219a9f6734647576e098e2e234e' 
  AND token = 'au8G18xyDPRIiEWVMl5MfCZ/6+qYo7HBtuYSjghOkhg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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