SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76124725e899e4e02e8ded5c3cac6ed3a7386f78f3e34ba9e4637b9dc4d5616b' 
  AND token = 'vx+OVBbjmfZUk0YM7lz+YgFhbMnNLPU/PtNEgQ7iJ90=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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