SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76dbbd639dc55e5abe3a2590dfd3074b7939a0183ee4d3d316d0e51357734370' 
  AND token = 'qN/Khprt4KjCb9voQpBpuHYAlj4NbRJ9ibtZEvyE5c4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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