SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6d7401a44513696a0246c50164a126015d15e95e9aa75c58797f4eb7099decf' 
  AND token = 'd2E1YqMnnMatdnO5WtsZ4m4iREK7sL1gI510YsUcEKY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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