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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a1fc9186915e933881bbc782815a5dffe915987a628730b78e174b6cb33dda93' 
  AND token = 'L3UedYpaBGfmm877VuMwEqQMzhV1MxpBNNuM50swBqk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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