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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7b01fb9368a778a0af02729bf4d503b77d15aad62300d76d5183dfccdee4e68' 
  AND token = 'tl2gHPjHKLbXu2GlI7hgs3IZ7uGXrFmyFLxgCJRD1WE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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