SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c18ad3405c6f8d3d0d09f1af3f87b2137b978ccca1438c18991d637f522e2855' 
  AND token = '+vzMcCF8+/IP7gHlzxYBBtiQeXq0kl6OwBd/2NBfhhM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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