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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ac4b88668d1e3a275418f92a195aef64fc1b0d260776a58870d9ff75ae6be385' 
  AND token = 'l+8qy9NxVP/Ef4ZnCHkGUAa+6dCRyr8/xOYgkLFEfkA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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