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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5f6c4d1651c5443fc9f20fa4294e5f6f5b68014f6a4fbb1b2d17f1a9a476c596' 
  AND token = 'pmEnUSU/JaIIqwi4byEu/Lesfi3FvXQm/W6z3hxxsAw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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