SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '948392cc7738b393a25d9051f9621eab984571c4f03440d52875d42bf0ef12ff' 
  AND token = '4t/kGySzLdHlEYRVeg+gFGRRy+whAmArKkNnwdzQUdo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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