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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '250bc06f983268f88ccce81ee087c8d917d4300acd6d650eb78e9646d77b10d2' 
  AND token = 'xn4Do/Cb1q+PgbsyzFWfs5/dXxVj6DeMur25skHPP7c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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