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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a81db33bcb018ad7345aa825239681da56594323776ae356cc332cde6633bb32' 
  AND token = '3iGeiH6ordLL/H/dvVL/dR6wFA9+RB5+2EUqITpGh6o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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