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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c66a54f7c5810dac578fc7268a8192553a0cdc1de319d2ba8f794ace482ac55b' 
  AND token = 'uu8AVddberBRBhudhqNB8dKT+MCUY31yVt9cOs9mejU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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