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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6fc3dfd985e77d635896a6569e8cc8cf058832691dfc00720c2303d392ff8b0' 
  AND token = '9Jw1ZWf2YcqPSuo2OTFXEl6QJ0OO90Y8z/Cw9dZcU4s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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