SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e8b335fa2fbac3c8773d053bc2ab50977cd1d2ee97ae7ff6b892603c399da9f3' 
  AND token = 'K+/IlnihDKKXToVT4LyHm6mKKZFVktqNc8yEDi/bSFw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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