SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6a3804dd42e7df5e24dad2f9e5b3652a122ac1945aac2a715e4907a97a40fb1' 
  AND token = '+/WSMwVkh59WQ71jvJH4Yzv/PBQwbiCQDEMKx5eXzH4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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