SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8c55855ef23b2547891ef9eea78c216cdbf971bab61a8e25b171db266804740e' 
  AND token = 'lL2ujKx0qCx0I8ixHYnukLJqGhiK47KB7ZAOcMMBhHA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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