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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd08e1ebc9c1b87a04f1eb5fd00d917ef29fd26350926c755ba1dcde4ba3f7b40' 
  AND token = 'vr166VCvGyEsAIzl52Uu+olFf5nliW+UGbi1kYpN2cY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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