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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4ff0cbc411d22e1ee19cef749bfac69d5412662d8839dd438cc70d617ad0d41' 
  AND token = '91/3TzslewD1WtRh73oBhZF9eGXwMQ7JZ1AYJv4pDM4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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