SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '815be47ce223cb64d15d48f848ff75cb8d9b982357de3c004158c37e938d43af' 
  AND token = 'hIC8sGjam5EJSRE6mtxaaWOG4/JjurkU2sEg73xAcvc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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