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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8b632606b22d293800d1ac45a1481a9aee7955c5b6d9919d10080beb4c7df15' 
  AND token = 'VQzQDydDVibork0llrErKnPZ9+MTj9RGAC1dcZmt3lI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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