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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '40757744a8d9d9b7a5fe1e31e7f0107e87018420376e0b7b6daa47a0325a995b' 
  AND token = 'D+vhimlZakGUEr5nuFRZQ3AjWGQbK6dhodN0gCdrtYY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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