SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e5a1a9a55855aabb011ca55608dfcc9383fde9282deba51b0aeb07f26e119935' 
  AND token = 'PoMRRxRxqcT7PznWjtxjBOHFcZamYjrLwOBiHtTHOEc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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