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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21b3542ab157b7c24bd5cd0b08941e5a7c8b2d01bf16d4a755e78467abc8fe8d' 
  AND token = 'TJHnjO5AV8OTLZfTt85sqTYkBNs9P3vXMRRzp42Okyw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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