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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d48037eaed194a0c09fc95244199fd35e10651805645f27866585b64afcfa00' 
  AND token = '8B1bMBCma6pz6fDOUe9HycGjg9kvKniKkDOuf0BQAVo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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