SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '951a708b878be6812014166b25eea357fa41c2504c741946f5284386e9f3a270' 
  AND token = 'G5+LZ1RL4tSBbG0rw5DZS3kFsOG+FpQ/pjqG5Dzwzeg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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