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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6f701a8c92da60b832fc58ad40b4cb55c15849ae940866498610799ab24ed57' 
  AND token = 'vLDtK/al5e+acpQ9/hYDlJDBwAd2nVeTnBw85MgY5R4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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