SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '765320d7fd64456b57ebe4a6825933b212b37fbfd90827c1b001e54268f5c650' 
  AND token = 'B6s8kZ92pTiKjlaF43YxueRBoiWml4pHMvfhLONAk58=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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