SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21746237e2f2782b4e8d3cfba717dacd1f0bf90aa7fa33d6244669e442078f41' 
  AND token = 'EfNhEwTJRblTbht4rm2XsS57MAqtrVq5a4ojAiCSBh8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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