SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd765b2e11a37f42304da26ea188c8ef82d08383bcae53be8d2555476158dfab3' 
  AND token = '4TTaUWPWE1uftAiaZRFZBN0YFnSCAtmh/yAQuMwJhn4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}