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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ffef90f57ce1990ece007f6c371e6b023ee12a1d0db29c60508c6d813665bb9' 
  AND token = '6qTcLS3QCRcfRxTnRsHVjhwYFoHp+NDE3sMdlWBDCOU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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