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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b3a9536a16d6a6bc7683c1ec392c4350c4c4ef410037f21cb813892bc88bddda' 
  AND token = 'UR3PvBzwfEOR6pjFINLqvsclCdd6Wz2+EbKzPN3N+UU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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