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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b255c2bc87d78b40002c5d1abdccd9659c0ca3bac971ddd6d6b7f21477587836' 
  AND token = '7NRvSWdmy5CcMDalZiZGxApHJxaQDY8pvHz6Ja/R0nk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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