SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8c3c3953a0dc37468d9befe17293547bb4fa0d4963cf5bcfdf84ca8d2906947a' 
  AND token = '3IedkOo2iYPUUjH6Sow6hw3pDTksRZbmeNgvJVwxjbY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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