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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc27ef60623f14a0b6a96e7fa293161c0c53bc1b31f060745cb2f80f5ec5fe5a' 
  AND token = 'rc4mdM0oEQ+sJQcIiJNGeEsNJG4DVadrIvSoY15kq3I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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