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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b68f0069c335e4af960a7853a1b7e65ae5973b54f4d6656d71f2765cff9be09d' 
  AND token = 'PoI9ZTyLo5uqj7CpBgLKXqp2n6QrnRwYbVfDRdZ4XnA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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