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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71add7256b5ca770574432c6cc314958beba9272beaa5aade8b572a85896f86c' 
  AND token = '/uCjhR5bK0zLBWKVWWrwmigpchJSZs2EtSjdLmSsImI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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