SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '088f6f7bb1df401bc737af212ed029909f3be4f002bf086fb486a5b307766c79' 
  AND token = 'CmYp2oyntPTvLGXj6b+IvTjseBPr2FWeiHHYSXHJYNw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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