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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6de61b3a7846621a0d7712fc8293adc2eaf3b4b409f8cba7f5cebec1892f11c' 
  AND token = '1sEOMN+vkRWhb2Z0FFWHLZfUWJQh4q5vAxNyPiROM8c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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