SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c031e72f21da95043438ce1934d686b51d26b8a587ae20212ea4302ba4524f44' 
  AND token = 'ALbMxkJbXge+aemqsVG0tqkXkr2rYY0UyZA3+aQmf5g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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