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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc578e0cf8b7c8c6694303ebc60daad2f5d5fddb950b0783c3663c3e9b8d4a21' 
  AND token = 'k1r76d0zwPqbXDdsrISsLVm2ZdJQPrl4qhZ+WSm5KZA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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