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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e6b39e812ca78493e3bb31bc064368c83d155e9d166cd9151a66e3668dfd8c9f' 
  AND token = 'xDMdat441SPcyxhOspKPs6254nbRVOebYfoTQQn98eE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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