SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7a7d84eb2d38c16b0b1a6fac9d4e22510cb6de9e7bb75ffc08003590def2f0c' 
  AND token = 'VkKUJXCJCwWnFFQvaAyBcqB7TCj/xlYv7oxIRufjxww=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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