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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3337e75a5742fa9917bb9fbd735c829736bd1bd53f4ffd688b7ac5eeb85b27c' 
  AND token = 'SKRxn8GCpMIr4sMfKMYcJZxeCb9K0OgJwoNIL7SVXag=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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