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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0375be5b9335962bda6dd8eca5e43ea019aece13d443165f7d5e4bc8b85e2a1c' 
  AND token = 'lj7t5LkkHmi+yJxGOEtgGB0qxhhuBw5VY9piyPu4wMU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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