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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a2aa3d34df3c715e9ffacad8958e330672830e31068298561b5df68fa87a75f' 
  AND token = '6nm7pQqESnRICOvkk8qlcQalZp6fLnj9daDxF9hGk9M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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