SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e28e57cb66728243079090b3d52a0a864e225d23caa3b8693493688df1a7ba7e' 
  AND token = 'ull+ZUhp65CvmHLZKn+q+41BFBalVqVzFnuQ/tDIrVk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00081

JSON explain

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