SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '266b7ff68bc9ef316244c8e597b429865a4904253b32787e53480146a8011b3b' 
  AND token = 'QQMY2O1rKjJILKCYx3BRf4hYMNBzlEnQmidgtUjObMU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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