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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21476bf28cc9b0cb18efc6dc69ace74d5141891a0e95d6eeb28a031fc80d1783' 
  AND token = 'tjrPh3K8GxONjnaRepNkDNqPI+1B9aqlEz4939scbIA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}