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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5f0e69bdfa7e6bc46f1bba3898526afae5fdca4ced1725b1d0ab9b3d66a02f51' 
  AND token = 'p/BfFo7NN0pKFoe9QhBkge5RP8tcEBTL9NKd9tCamDg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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