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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '326beb8cf75608a8ffbbc9ae06a4f50721fce4383d20ccc240f594052bfc855f' 
  AND token = 'f6SQT9MC+Uj9f2MD5Uq3cQvs27eDz+DdSBXXXFndKcw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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