SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bea51ad74c4d9b7bf364633afdd2857771231de794bdca62d86233b91b17ee09' 
  AND token = 'MGnU3YL1lkgpx/VTdJpNKiOxpUcUOMpXm48uTvamqWI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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