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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a91b9f81e09a911ca2baddf8c57822786eae452c618e2d2d8f414d9ee051d44c' 
  AND token = 'JNZLmTpxbrcBYNYAq4L4R2FY/CbLCp/gFTRBhBj2d3M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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