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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51b9840ef62285ad3dc1170cd3dbc12ff253beb3d4892767e215bd0d85588e9a' 
  AND token = 'rbRxAn5/pTpRsYUcgNqd50Vi2IuyEa2WBnVwNwSMc0Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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