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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8c124534c1a92383f88c1f7b678bdd0f94f2fccac1c9812c799248f6dd61a260' 
  AND token = 'kV5CHnNb9eo6pzbzFkBZTnD0mHYR4OrtFgIv0XPVzZA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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