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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '561d28bad1a973194b0f584cce35f34b01401a834897d4dc2fffef1addfd41a1' 
  AND token = 'pSoXWYVNF38muymIJR3rOiOt8np7wPux++SZkYcVo+g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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