SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cf97a2104bef212f0e11dfc65037c4b2c16b0aed814e20a5559b576d4e9849c3' 
  AND token = '6r3krzNOp4VnjPBivVkqx9IwOPi5+zVcYt+fnDhN/kY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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