SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '90d93a55293dd7f4bc40975224a67b170be822a4b8b59c2d328004986a8e51d9' 
  AND token = 'Rj3LzBfjh6lLb/WJKNSySXF7SI8ZBq9mAoYi3yu+qkI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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