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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b68b6eb516ea1510dd88079b371c9bbd40e42f07617a2bd11b770ff5b402bab6' 
  AND token = 'IaJrkPSFV0yDkVopZzRDe+GkvRMfx9LwhQ4yyt9I8a8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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