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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8d100612ddc13cb39e1be267dce78bd9bafe53a96c4bfc31438299d84e68c1e' 
  AND token = 'Pk/Cw8CF4y7rL55lx6msh8firWpO7Ipsh1jf1z1ZGwo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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