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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '16d6b0ebc451c56ba63de5645ba7cd9ce024b1f3fcab4d4c0b84079f20e2dc1d' 
  AND token = 'KMe8fWcP0u9bAB5E+VXdUGVagDiMOv9+3YzPyrFT/ME=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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