SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '091f9ba70416cc61bc7b1e90af112266f1ea27792aebc3be98e4c1c18cde560c' 
  AND token = 'QwnjJCsGsiJlYv+eVryp1EmFIeHsuvSyEwWoR3WO9BY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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