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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'dd283f082812a09a382a8ba4476657796ca51d7b645e7a78f6818499907ad3d9' 
  AND token = 'WtABVGBlW1LVemOpValB3cUznvloKlqOWtTdLwKjik4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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