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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fb5d99c70d8f5c7fd1980b4d2bc34750adec5f1a6d33d30d0448009a3c9b50d4' 
  AND token = 'IEiiBFnKz39RhmAeSPFqWnyjZeNUUkYj/jSvpO2RaF4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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