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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fe1627a3827c29c7573195c5cce4fcf7fb20da8dda4a4033a9615d7560f9318' 
  AND token = '1kkVfPHmaGzOikWTTsa0ZdwxaNIvTXfNWS8GReYa7Nc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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