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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b25c63bf7b29ff3ee4ae9641f1faeb5cb335bbe7a33b30579a1a6c465c637d58' 
  AND token = 'K/mW+yg/giLG4dxcMjfh7ge2WniBKfKP6i+zfDIU9VA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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