SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c81ac000ed2934d77136d1420d22d2a5c45729cbb604e259a0637654e87a931e' 
  AND token = 'agUBjNIvaLD3lVo18M2StK9dV+ofkLDNnSNS5gkcJ84=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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