SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d51eea888dac7b5003e1445850d2ef375f632c9844c812fd90a802e6c16a773' 
  AND token = 'Szrg6BrKYkWPJZlz+Npze0cEsqWkjbINH41bpddaw0k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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