SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1c167790d150c3fe131908bd7096f1f54610515b6eed821a602ac0388abbb752' 
  AND token = '2j1K7o5kypwlkQVC9NuzTgxOU3BLvQWCjC6xZwwpSnY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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