SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '37e4639aff4275284f847bd9ee12d34f9b279fd7efe8eca735cd2afc892fc7a6' 
  AND token = '+AOxPnaTEWuRUYTq/d9SZKuZwyvfsD2hfiA8wiC+gJM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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