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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8ec2ab54fb3ab6271d8c6c24c94fb0cf05cd639cf9e32b8c9feda1570021456' 
  AND token = '96nc5iNsj9kLQjC8rTaA8nSnSXf1UeT8elUaGL4q2ts=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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