SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3e71540816c7a8036079957ecc6371faf7a9f6af7a75f4c8eacaa0082d06a9c4' 
  AND token = '8clPJaAFN8NKPMbFVn+uVPRFtmmEBphJuz+s6DVbskg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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