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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3e3fbb52fc64ce001e55f92da25dbf07e90df22a2f71678e77eeeb14e0ca028' 
  AND token = 'QGPMvbz8DvdHY7PaDVgxfP7RYOmXzcEYY3BzVXmDFLY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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