SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81f297945acafb89c28cdff4fd6059298fda3f96c8790ba93c995cd3ccbbb9b7' 
  AND token = '8PuZalXngxVtxf5drWx6rAc3iIdFiHQjPa1lmhJZL4w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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