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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21c290d4c8218c1f3900c744f7c27d9f4bfc6eba075219f778310d3efe4dc41b' 
  AND token = 'O3cZYmdehsD+uiHcdaKeb4WrlGl2VRMbYn9dwS/scQA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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