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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f4380bb9489089119530b9fc937f0ce8b70af25ea16e92043666957805a1496b' 
  AND token = 'jnlkBn329dtz3xY3Awae9fo0bcKrY83D2mReR1PEVDM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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