SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5e40eb7311a5dd878b81d579cb7b493cb775983262ed8943383e60ab65497317' 
  AND token = 'WZTekEGE2JYU8ATcJ1cAfmN1G88WoVVlSnbBB4eeIG8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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