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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '973e5b5ece7e5f37750a43eb559acd0672c1f0ae15a28a7a60f2cd9442647b7f' 
  AND token = 'Ff4W08BCDqFiJ84+rmRES3bIyGfXBEDXdFHDetkjl3g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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