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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a735d4e3b43180f1d0be35d895a0c51293d9192387d8bcaaf43e46f20051c7bb' 
  AND token = 'v/CUDj/3E7BP6JXot+imTwbFT4ei29CjEThBkIRmmmk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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