SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '501aead9294007268670a4abda4f87820eddce2a8203f6737af5def65284381d' 
  AND token = 'rLGhBomGDqLCzNzVNBZUUN1N6vkghp1ez5gYnuNxxV8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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