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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c6305918ebc9fc21162602616273cb878bafa939a7102de53976196aa8aa90d1' 
  AND token = 'yF1UYESjcuhdWRoTh28AHWuE5mDPTA9GvDeIuRw3OUw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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