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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c615123de48653d96d248b3f0892742424084e35f401f4c26d780318585629f3' 
  AND token = '1Ql7AfvVLt9/Fu7Hjjpj3hMcvDB8XbcXIlvSRent+NA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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