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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6cf980716716202eaf76b16a49a7ef5b154a70f8e0235d3a90ee4f83b6ca8d2' 
  AND token = 'YxiWtlnl47dHnILLx6vyD1qXPwwy0Kt6+/COsB2G7uE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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