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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef4a3b3a2875315dcefde743822979d5a4f70efe1620972dfb8dc3740f93f0b7' 
  AND token = 'tXc1OZ0MVHA8dl4QqplwvwSVpr8XR+Qy4+gfv/iqHCw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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