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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4321a33e5580c845f5a345581d3876da55bb8cf864d4479a7e2ee17d1071578' 
  AND token = 'XmdP0j/Qo7zF3Rn4KLy9OKn1OcEbBrXjG7CtW/m53Hk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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