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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6dfd1e1fccee3237d7dc9b4a3470d59861b8ee504dfdcaec725884b8aa2f3421' 
  AND token = 'mXN2M2+77hCbOYnKWgeYAow3bG/01fOUnNq4zB+5Sj8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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