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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '751bc9943ce105f2561a8547ef5d011e067b3084c19d868955e4bb9c71a79c9c' 
  AND token = '+begZu5cfddyRqrxy8QfVMdISu3poZLyiYX2fRh04u4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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