SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8fd24f035186b993377c567a6ee3ccbc82d1a9d2c8b0a6d911bf6b300cbe0e9' 
  AND token = 'rxXy9fqwdSfZcgsbXw/Gj4o2I8gNGpjr2VBZYkSTpWE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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