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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7b7bf291415043ed635002365368051bc496142108afe1c12966d26be67d4842' 
  AND token = '7qlvlKoviQkaZtloZ0vz8FAGTEQ0KXbCrcRY03DMyKg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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