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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8bf890889ec0c7201829c927f5ed1308aa230ddb749f68d26a4c3c55fc66adb' 
  AND token = 'WpEm3mcyeNnRzJft+lxdE1aaBvVCdEWzkOlU4Y4M3QM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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