SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3ec1d0edd8492f28a9d20895bda46fec51156c2a6505e8465068c59fdb217de' 
  AND token = 'Duh9qiI1mYOOpFXQyqLwwIFCPlOBUAkJ+/hKR1ipSLw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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