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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18ef7cd6c02f03356d83e8e3f85a41e874bd2086e1108926b0efee5aed8bc847' 
  AND token = '91o37gpouiugZpWTTju9+0xxGw0PJB5znuVK4GCG/5c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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