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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e4cc5a6ae309587c13c5be5e2bed6ee0be621c82ebbec347ddb4efe1dba7342' 
  AND token = 'q6Xz3pfslzOMgsEWzGsJzoiEmlt/MtfSmwH04wOA8tY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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