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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a4bdfc21011493a4e91245a956cb1bb1990d5b5a22d2e378bc1d201fb6ea1a5f' 
  AND token = 'QYzxs2sSN82D+kcu+9XuCmzhmhFjYaqiCSg/+x/FPSw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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