SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '621a48835781e351d3210bdb690f4c3774c1a1cfe59597d0f6d3a29307493364' 
  AND token = '/Z8bxGpysi1zbnrjS8VlpoEVOFDBAJnqIFQdiqc85Ms=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00040

JSON explain

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